ZURICH- Most Swiss oppose a referendum campaign launched by the far right to end the free movement of citizens from the European Union, a poll published on Sunday found.

The referendum drive reflects unease with the influx of foreigners, who now account for a quarter of the Swiss population. But imposing limits on EU citizens would violate bilateral accords that enhance Swiss access to the EU single market, the lifeblood of the export-led Swiss economy.

A binding referendum is expected in May on whether Switzerland should take back unilateral control of immigration, if necessary at the cost of abrogating the free-movement pact that took full effect in 2007.

The vote was put on the agenda by the far right People's Party, which is the largest in parliament and has two of seven seats in the federal cabinet.

The referendum under the Swiss system of direct democracy is being billed as Switzerland's "Brexit moment". 

A Tamedia online survey of around 11,000 people across Switzerland found 58% were against the idea, 35% approved it and 7% had no opinion. It had a 2-point margin of error.

Battling the referendum campaign is a priority for the Swiss government, which has struggled to put relations with the surrounding EU on a new footing.

Brussels wants the Swiss to endorse a new treaty that would have Bern routinely adopt single market rules and create a more effective platform to resolve disputes.

The Swiss government has dragged its feet for months while it tries to forge domestic consensus on how to proceed, annoying Brussels and triggering a row over cross-border stock trading. 

The treaty ran aground amid opposition that spanned the normally pro-Europe centre left to the anti-EU far right. Critics say the pact infringes Swiss sovereignty to the extent that it would never get through parliament or pass a referendum.

The Tamedia poll found 39% of respondents wanted the treaty renegotiated, while 24% wanted it signed quickly and 24% wanted it rejected entirely.

Swiss voters in 2014 backed quotas on EU immigration, but parliament skirted a crisis with Brussels by instead giving hiring preference to people registered as unemployed in Switzerland. This angered the People's Party and led to the new referendum push.

(Reporting by Michael Shields; Editing by Alison Williams) ((zurich.newsroom@thomsonreuters.com; +41 58 306 7336;))