Support for the UK Independence Party across Britain has risen to its highest level, consolidating its position as the third most popular party in the country, according to a new poll for The Independent on Sunday.

Two weeks after Nigel Farage's party achieved its best-ever result in the local elections in England and Wales, a ComRes survey shows almost one in five people plan to vote for Ukip at the next general election.

Labour has dipped to its lowest levels since Ed Miliband became leader, down three points to 35 per cent, the Tories are down one point on 29 per cent, while the Lib Dems remain stuck in single figures, at 8 per cent.

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Ukip's support in Scotland now rivals that of the Lib Dems – although police had to rescue Mr Farage from an angry crowd in Edinburgh during campaigning on Thursday. Ukip's overall ratings have risen four points to 19 per cent in the past month, despite David Cameron's efforts to wrest back control of the crucial debate over Britain's relationship with the EU.

The polling also shows that 46 per cent of people would vote to leave the EU if a referendum were held now – in line with Ukip's central policy of withdrawal. Only one in four would vote to stay in.

However, voters would back remaining in the EU by a margin of 43 per cent to 24 per cent if some powers were returned to the UK.

The Prime Minister last week published a Bill that would pave the way for a referendum on whether the UK should leave the EU, in an attempt to placate party members who have been dismayed by the coalition's failure to address the issue in this Parliament.

Pro-European Conservative MPs yesterday vowed to disrupt these pacification attempts and defy party orders to support a "doomed" European Union (Withdrawal) Bill, which will set out the terms for an EU referendum by the end of 2017.

"I would be very reluctant to support this doomed legislation at the best of times," one senior pro-European Tory said last night. "It is a sop to the right, and even they must be aware it's an exercise in futility."

Another Tory MP, who has argued for a renegotiation of the UK's relations with Europe – while remaining in the EU – said the Bill was "a waste of everyone's time".

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"I will refuse to take part and I don't think anyone can seriously complain when I don't," he said. "This is a face-saving exercise which serves no one's purposes. For those who want a referendum it might be a way to let off steam but with nothing to show at the end of it."

The poll provides some consolation for Mr Cameron, as almost half of those asked said it was important that a party seeking their vote at the next election offered a referendum on Britain's membership of the EU.

In January, the Prime Minister set out plans to renegotiate the UK's relations with Europe and put that before voters in an in-out referendum after the next general election.

However, 114 Tory MPs last week voted in favour of an amendment to the Queen's Speech, regretting that the Government had failed to include legislation on an EU referendum in its legislative agenda for the coming year, largely due to opposition from the Conservatives' Lib Dem coalition partners.

Stephen Dorrell, a former cabinet minister and pro-EU Tory, last night said he was comfortable with the new Bill, although he conceded that "we have reached this position rather inelegantly".

He added: "I expect to vote to stay in the EU, but I have no fears about putting the question before the voters. There needs to be a review of the relationship between Britain and Europe and the practical politics are that we are going to have to have a referendum to sort out a solution."

Labour's six-point lead would translate into a 74-seat majority at a general election, with the Tories losing 86 seats. The Lib Dems would lose 34 MPs and be left with a rump of 23. Despite 19 per cent of voters pledging to back them, Ukip would not win any Westminster seats.

Only one in four voters said Mr Cameron was turning out to be a good prime minister – the lowest number since ComRes began tracking this. Half of the British public, including two-thirds of Ukip voters, disagreed. Half of those questioned agreed that Mr Cameron had the authority over his party required to be an effective PM. One in three people agreed that Mr Miliband was a good Labour leader, the highest since ComRes began tracking this statement in December 2010.

The Conservative MP Nadine Dorries, who had the party whip restored to her last week after it was suspended during her participation in I'm a Celebrity ... Get Me Out of Here!, last night called for a Tory alliance with Ukip at the next general election, saying: "It's the only way to beat Labour in 2015."

Ms Dorries also said that the Government was lying about bringing down immigration. She told The Sunday Telegraph: "We lie. We say to people we are bringing immigration down. That's a lie. People are not stupid. We have open borders with Eastern Europe. They see Eastern Europeans flooding in and taking the jobs of blue-collar workers and taking away from their quality of life and job security.

"They see we are about to open the borders to Romanians and Bulgarians; they have large organised crime rings. You know in Cambridgeshire, a rural constituency, I think one in four rapes is committed by an Eastern European." She added: "We need to say that we are going to stop Eastern Europeans coming into the UK because we want to protect your jobs and your standard of living."

ComRes interviewed 2,017 UK adults online between 15 and 16 May 2013.

Brussels bonus

Meanwhile, what has the EU ever done for us (apart from delivering nearly 70 years of peace)?

Farmers

The UK exported 114,000 tons of beef to EU nations in 2012, 95 per cent of our total beef exports. After the BSE crisis subsided, the European Court of Justice ordered France to resume imports. By contrast, the US retains an embargo.

Holidays

Flights are affordable to many. The liberalisation of European air travel has driven down the cost, allowing companies such as easyJet and Ryanair to flourish. EasyJet employs more than 5,000 people in the UK. All this, plus the right to four weeks of paid holiday per year and free emergency medical treatment abroad, has changed the way we take holidays.

Rivers

The cleanliness of Britain's waterways has dramatically improved following several EU directives. The Thames, once declared "biologically dead", is home to salmon, sea trout and otters. The Wandle, Stour, Mersey, Dee, Wear and Taff are among other rivers to have benefited from the legislation.

Rail

The high-speed rail link from London St Pancras through Kent to the Channel Tunnel provided 8,000 building jobs. The £7.3bn project is estimated to have created a further 50,000 jobs, delivering £20bn in economic benefits.

Criminals

The extradition of suspected murderers, rapists, human traffickers and child sex offenders has been enabled by the European Arrest Warrant. Hussain Osman, one of the plotters of the failed 21 July 2005 bombings, was extradited from Italy. John Murrell, a convicted paedophile found in Ireland, and Jeremy Forrest, who was arrested on suspicion of abducting 15-year old schoolgirl Megan Stammers in France, were swiftly brought back to the UK.

Sex

Gay sex was decriminalised in Northern Ireland in October 1982. Jeff Dudgeon filed a complaint in 1975 with the European Court of Human Rights after being interrogated by the Royal Ulster Constabulary about his sexual activities. The court found that Northern Ireland's criminalisation of homosexual acts between consenting adults was a violation of the European Convention of Human Rights.

Nature

The Eden Project has benefited from £50m of EU funding since 1998. It has brought an estimated £1.2 billion boost to the Cornish economy, employs 500 people and supports 2,000 peripheral jobs in the area.

Phones

The European Parliament is behind a 70 per cent cut to the cost of using a mobile abroad. Prices are set to fall further in July 2013 and again in 2014.

Adam Barr