Coalition struggles to maintain united front

Simmering tensions between the Conservatives and Liberal Democrats over immigration and electoral reform emerged in public yesterday as the coalition struggled to maintain a united front.

Vince Cable, the Liberal Democrat Business Secretary, appeared to question the Tories' flagship policy to impose a cap on the number of migrants allowed to enter Britain from outside the European Union.

"It's no great secret that in my department – and me personally – we want to see an open economy, and as liberal an immigration policy as it's possible to have," he said. "We are arguing, within government, about how we create the most flexible regime we can possibly have, but in a way that reassures the British public."

Mr Cable was speaking to Indian journalists before joining David Cameron on a visit to India, where the proposed cap has come under fire as it could prevent Indian businessmen coming to Britain. The US grants visas to Indian entrepreneurs and residency rights if they create jobs.

Meanwhile, as the Commons began its summer break last night, 44 Tory backbenchers launched the biggest rebellion since the coalition was formed by urging ministers to scrap plans to hold a referendum on the voting system at general elections next May on the same day as elections to the Scottish Parliament, Welsh Assembly and English councils. They signed a Commons motion warning the double vote would "allow other issues to cloud the referendum debate". The Labour shadow cabinet added momentum to the rebellion by saying it would vote against a bill introducing the referendum, claiming it was wrong to also include plans to reduce the number of MPs.

Among the Tories who signed the rebel motion was David Davis, the former shadow home secretary, who has reportedly dubbed the partnership between Mr Cameron and Mr Clegg the "brokeback coalition" after the film Brokeback Mountain about two gay cowboys.

Edward Leigh, an ex-minister, told Mr Clegg at Deputy Prime Minister's Questions the proposed timing for the referendum was "extraordinarily dangerous". Mr Clegg said holding the polls on the same day would save the state about £17m.

Labour is gaining from unhappiness among Liberal Democrat voters about the party's coalition with the Tories, a poll by Ipsos Mori for Reuters suggests. It shows Labour up seven points to 38 per cent – just two points behind the Tories on 40 per cent with the Liberal Democrats down to 14 per cent.