Freedom of the press is so vital to US society that this occupation is the only one expressly safeguarded by name in the First Amendment to the Constitution: “Congress shall make no law ... abridging the freedom of speech, or of the press.”

Without a free press, all our other freedoms are endangered. It is our best defence against tyranny.

With that protection comes a deep responsibility to scrutinise those in power and to report fully and fairly. But to fulfil that responsibility, news organisations must also insist on maintaining the highest standards of credibility.

In recent months, the media has come under withering criticism. Some of this has been unwarranted, but some has been very much deserved.

Specifically, the allegations of deeply disturbing predatory behaviour inside leading news organisations, including CBS, Fox News, NBC, NPR and The New York Times, have shaken public faith in the media.

What I and many others who work in the media know is that these organisations are not alone, nor has the full range of media wrongdoing been detailed.

One major reason that journalists and the public have not learnt all the facts: non-disclosure agreements.

Many broadcast news organisations use NDAs and confidentiality clauses to muzzle current and past employees.

If an employee dares to speak out to expose media wrongdoing, a news organisation and its parent corporation will unleash a legion of lawyers.

Particularly in television news, no individual has the financial resources to combat a Comcast or a 21st Century Fox.

Why would employees sign an NDA? I’m a lawyer, and over the course of more than 20 years at major news organisations, I signed multiple NDAs.

They were routine, and when I signed them, they seemed reasonable. I fully expected the corporations I worked for and their executives to follow the law, to fulfil their responsibilities and, yes, to act decently.

Why would a news organisation muzzle an employee to hide bad behaviour? Weren’t we all on the same page, working to shine a light on abuses of power?

I realise now that my basic assumptions were wrong. It is absurd to require NDAs for employees of broadcast news organisations — whose right to speak freely is already protected by the First Amendment.

Moreover, what is so secret in a news organisation that it needs draconian protection? News-gathering isn’t like sharing Coca-Cola’s secret formula with Pepsi.

There are no real trade secrets in TV news. Everything I did on my shows on three different networks, from segment times, to interviews, to video clips, was immediately in the public domain.

The only thing that needs hiding is bad behaviour, which, sadly, is hardly limited to sexual harassment.

Further undermining their credibility, the same news organisations that insist on muzzling their employees pursue some of their biggest scoops by encouraging outside sources to violate their own NDAs.

CBS was happy to have Stormy Daniels violate the confidentiality clause in her settlement agreement and go on the record against President Donald Trump.

So my question is: Has the network released all its employees from their confidentiality clauses or NDAs? I would love for CBS to tell us.

But this is much bigger than a splashy stripper suing the president.

If news organisations didn’t press sources to reveal secret information, we wouldn’t have the Pentagon Papers or Watergate or uncover government duplicity such as Iran-Contra or the truth behind the Flint, Michigan, water crisis.

Yet when news organisations and their executives are the perpetrators, whether it is sexual harassment, discrimination, unfair hiring or firing, or other actions inconsistent with their obligations under the Constitution, they seek to hide it.

When news organisations themselves stray, suddenly transparency and free speech are not so appealing.

Too many media organisations seek to resolve their bad behaviour in secret, via arbitration, rather than in court, where proceedings are public.

The settlements, usually including confidentiality clauses, are designed to be sealed. And when there are multimillion-dollar payouts, among those kept in the dark are media company shareholders.

As for the industry argument that without NDAs, employees would wrongfully disparage and tell lies about the media companies’ works, the networks and other organisations have plenty of legal remedies.

If news organisations want to honour their constitutional responsibilities, do their best job and restore some lost credibility with the American people, they need to do the right thing: release all current and past employees from their NDAs (except when they involve the rare legitimate business secret) and move disputes into the open.

Justice Louis Brandeis’s quote — “sunlight is said to be the best of disinfectants” — has become a maxim because it is true.

If news organisations don’t move to ban NDAs, it’s time we all ask: What are they hiding?

Greta Van Susteren is anchor of Voice of America’s Plugged In With Greta Van Susteren