There is a conceit among many senior editors in the United Kingdom that Britain has “the best journalism in the world”. At its best, certainly, British journalism is very good indeed.

From the sober analysis of the Financial Times and the Economist to the tub-thumping of the tabloid press to the BBC’s worldwide reputation for accuracy and impartiality, the British public have access to a healthy mixture of domestic, foreign and investigative reporting. On many occasions, democracy has been well served by journalists who make important stories accessible and hold power to account.

At its worst, however, journalism in Britain can be truly awful. Five years ago, much of the world was rightly shocked by revelations of phone-hacking on the Rupert Murdoch-owned Sunday tabloid News of the World. The subsequent judicial investigation into the culture, practice and ethics of the press, led by Lord Justice Leveson, exposed the tasteless practices on which some British tabloids had come to rely: the invasions into personal privacy, the gross intrusions into private grief. At the time, it seemed like a new low for the industry. If the Leveson inquiry revealed the tawdry side of the media business in Britain, however, the Brexit campaign has featured a different kind of journalistic abuse: contempt for basic norms of truth and accuracy.

In the lead-up to the June 23 European Union referendum, British mainstream media failed spectacularly. Led, inevitably, by the viscerally anti-EU Daily Mail, Sun, Daily Express and Telegraph papers, most of Britain’s national press indulged in little more than a catalogue of distortions, half-truths and outright lies.

It was a ferocious propaganda campaign in which facts and sober analysis were sacrificed to the ideologically driven objectives of editors and their proprietors. The interests of readers, much less the interests of British democracy, were barely considered. Three days after the vote, I spoke to a Labour Member of Parliament who represents a constituency in northern England with one of the lowest proportions of immigrants in the country.

Despite this, a majority of her constituents had voted to leave the EU. Why? Mainly, she said, because they were convinced that waves of immigrants would soon overwhelm their communities, take their jobs and undermine their way of life.

They were particularly concerned about the looming, massive influx of Muslims, given the imminent European debut of Turkey — a country that stands no chance of joining the EU in my lifetime, let alone in the next few years. How did things get so bad? In part, you can blame the internet, which has gutted traditional business models of journalism around the world. British journalism has been particularly vulnerable: for historical and geographical reasons — partly owing to early industrialisation and partly because of efficient distribution networks in a small country — Britain has long enjoyed the largest national press in any mature democracy.

Nine national newspapers — ten, until March, when The Independent went online-only — still battle furiously for eyeballs. This is, in many ways, for the good. But this frantic competition for a diminishing pool of readers and shrinking advertising revenue, particularly at the tabloid end of the market, partly explains why some publications have been willing to sacrifice basic journalistic norms of accuracy and respect for privacy.

But a second, equally powerful reason is unique to the UK: the passionate right-wing ideology that drives many of those newspapers.

The country has a long history of explicit partisanship in its journalism. While there has always been a predominance of right-wing papers — at times, very right wing: the Daily Mail famously supported pro-Fascist groups during the 1930s — in the past, this was partly balanced by the mass circulation of the Mirror newspapers. But the Mirror’s decline has been precipitate; the Mail’s online dominance, on the other hand, driven by its embrace of celebrity news and photographs — mostly of young women in various states of undress — has enhanced its popular and political influence.

Led by the Murdoch-owned Sun, the Daily Mail, the Daily Express and the Telegraph, with the Times — also Murdoch-owned — in a supporting role, the partisan Right now overwhelms the comparatively insignificant presence of the Daily Mirror and Guardian on the Left, especially with the left-of-centre Independent now relegated to an online-only presence. During the referendum campaign, this toxic combination of uncompromising devotion to a political cause and contempt for the truth played a significant role in leading Britain down the Brexit road.

In a June 18 blog post, journalism blogger Liz Gerard compiled a montage of front-page headlines to demonstrate how the constant reiteration of words such as “migrants” and “borders” in large, bold font systematically ramped up the xenophobic message.

“Turks, Romanians, Iraqis, Syrians, Afghans, Albanians: millions of them apparently want to abandon their homelands and settle in the English countryside — and only leaving the EU will stop them,” Gerard wrote. “No claim was too preposterous, no figure too huge to print.”

The tabloid campaign against the EU itself — its faceless pen-pushing bureaucrats, its absurd regulations and how much it costs the UK as an institution — lent itself perfectly to the oft-repeated Leave mantra of “Take back control”.

Perhaps the most egregious example was a front-page Daily Mail headline on June 16 — inevitably repeated by the Sun — claiming that a truckload of migrants had arrived in Britain demanding, “We’re from Europe — let us in!” The story ran despite video footage that clearly demonstrated the new arrivals had informed officials that they were, in fact, refugees from Iraq and Kuwait. In a futile attempt to demonstrate that they aspired to some notion of journalistic integrity, the next day’s paper carried a “correction” consisting of 54 words at the bottom of page 2.

This was a much repeated pattern throughout the referendum campaign: journalist Hugo Dixon, who founded a pro-Remain fact-checking site called InFacts, drew attention to both the number of inaccurate stories and the chronically inadequate “corrections” relegated to inside pages. The problem was compounded by the sheer weight of anti-EU press. According to a Loughborough University study, once newspaper circulation is taken into account, only 18 per cent of media coverage was pro-Remain, compared with 82 per cent pro-Leave.

It is difficult to prove conclusively that this constant drumbeat of headlines directly influenced voters’ decision-making. What is clear, however, is that it influenced the national conversation and, in particular, played an agenda-setting role for broadcasters, which in Britain, as in most of Europe, are bound by strict impartiality rules and are therefore more trusted by consumers to provide a nonpartisan approach. Remain campaign strategists were confident that the message of economic risk would succeed — as it had in the Scottish independence referendum — but they did not factor in a deeply hostile press whose slogans served as an echo chamber that broadcasters could scarcely resist.

This echo chamber was particularly evident on the vaunted BBC, which, by an unfortunate coincidence, is immersed in negotiations with the Government about the renewal of its ten-year charter — always a tricky and delicate task. As a result, its normally self-assured journalists have been obsessed with “balance”: any argument that receives airtime is accompanied by a counterargument, however patently absurd. This silliness was on display, for example, during a broadcast on the highly influential Radio 4 Today programme, which featured an eminent scientist on the huge scientific research risks of Brexit. She was then “balanced” by a marginal and wholly unrepresentative cancer specialist, who had previously stood as a candidate for the anti-EU UK Independence Party.

Overall, the BBC’s EU referendum coverage was much more inclined to follow rather than lead. Film director Lord David Puttnam, the former deputy chairman of Channel 4, a competing broadcaster, memorably described the BBC’s journalism during the campaign as “constipated”.

In her post-referendum media round-up, the Guardian’s Jane Martinson revealed that, within an hour of Leave’s declaring victory, Sun editor Tony Gallagher told the Guardian: “So much for the waning power of the print media.”

There was a further twist a few days later, when, on one of the most dramatic days in British politics, prominent Leave campaigner Boris Johnson, long considered the most likely next Conservative leader, abandoned his leadership bid. A leaked e-mail suggested that, among other obstacles to a successful bid, he did not have the support of Murdoch or Daily Mail editor Paul Dacre. Even in the age of social and digital media, which so many commentators believe will democratise communications, old-fashioned media proprietors and editors still serve as political kingmakers in Britain.

Can any of this change? In the aftermath of the phone-hacking scandal, Parliament did, in fact, accept Leveson’s key recommendation: that the press’s efforts at self-regulation should be periodically scrutinised by an independent body to ensure that it is abiding by its own Code of Conduct — whose first rule is that newspapers should “take care not to publish inaccurate, misleading or distorted information”.

A Leveson compliant system would include regulatory sanctions for errant publications, such as equal prominence for corrections and fines for systematic code breaches. Had such a system been put in place, perhaps Brexit coverage might have been different. The kind of deliberate distortions that featured repeatedly across most of the tabloid press may have, at the very least, been discouraged by a regime that would oblige newspapers to print a front-page headline correction to counter a front-page headline lie.

In any event, the new Conservative government, under huge pressure from the same press barons who undid Johnson, has stalled on implementing Leveson’s recommendations, and the British press today therefore feel free to break their own industry code with as much frequency and impunity as before 2011. To deflect criticism, they have established a “new” regulator, the Independent Press Standards Organisation, which is owned and run by the leading publishers. As the referendum campaign demonstrated, the IPSO has been ineffectual in holding its newspaper members to account.

Those same commentators who preach the revolution of social media also like to cite new media such as BuzzFeed, Vice News and other online outlets as examples of greater plurality and more opportunities for journalists. These are all welcome additions, but so far they have been unable to compete with the legacy of traditional news brands, which are extending their online presence. According to some sources, the entertainment-focused Daily Mail website, which attracts upward of 200 million global visitors every month, is the most popular English-language site in the world. Perhaps that will gradually change. Meanwhile, broadcast journalism still aspires to the highest standards of accuracy and impartiality, and another hope lies in detaching those broadcast newsrooms from their mind-numbing dependency on agenda-driven newspapers.

All of these changes, however, will be gradual and hardly constitute a journalistic revolution. Meanwhile, it is hard to avoid the conclusion that Britain’s mainstream media failed us at a time of greatest need, with political consequences that will reverberate for decades.

• Steven Barnett is professor of communications at the University of Westminster