ZURICH (Reuters) – A campaign to anchor bank secrecy in the Swiss constitution has failed after its organisers could not muster enough support to force a referendum.

The government said in a public filing that a campaign started last year by the Ticino League, a party from Switzerland's Italian-speaking south that is heavily dependent on financial services, had not gathered enough signatures.

Referenda are common in Switzerland and citizens need to collect 100,000 valid signatures within 18 months to force a national vote. Switzerland's tradition of banking secrecy that has helped make it the world's biggest offshore wealth management centre has come under concerted attack in recent years as part of a global clampdown on tax havens.

The campaign entitled "Defend Switzerland — bank secrecy must be in the constitution" was launched in March 2009, just after Swiss authorities ordered UBS AG to hand over names of US clients suspected of dodging taxes in order to settle criminal fraud charges against the bank. Later in the year, Switzerland said it would hand over details of about 4,450 UBS bank accounts to US authorities.

In June, the Swiss parliament finally backed the UBS deal, ending nearly a year of uncertainty that threatened the bank's recovery after a government bailout during the financial crisis as wealthy clients fled.

The two houses of parliament agreed not to hold a referendum on the UBS treaty — originally demanded by the right-wing Swiss People's Party (SVP) — which would have prevented the handover of the client accounts on time.

The Ticino League had sought to amend the constitution so that Swiss banks had to keep their customers business secret and could only hand over information to authorities with their clients' permission.