Ukip is poised to inflict a humiliating by-election defeat on the Tories in a result that leader Nigel Farage said would signify a 'landslide' in British politics.

The vote, which is set to take place in October or November, was triggered by the defection by Douglas Carswell from the Conservative Party. He said that he would resign his Clacton seat and fight the ensuring by-election under Ukip’s banner because he had become disillusioned with Prime Minister David Cameron's stance on Europe

And a Survation poll for the Mail on Sunday released today gives Mr Carswell and Ukip a massive 44 point lead over David Cameron's party.

It put Ukip on 64%, with Mr Carswell's former party on 20%, Labour on 13% and the Lib Dems on 2%.

Mr Farage has predicted that a win would result in "more and more people coming over to us".

Mr Farage told the Sun on Sunday the stakes were high in the contest for the Essex seat.

He said: "This is the moment. If we win the by-election in Clacton, it will create a landslide in British politics.

"If we lose, then selling ourselves as a party that can win a significant number of seats will get a lot harder."

Mr Farage added: "If Douglas wins this by-election, then there will be more and more people coming over to us. We could end up holding the balance of power by next May."

That was "utterly dependent" on the Clacton result, he said, but added: "I'm going to keep playing double or quits until I lose. But if I win three more hands, we'll be out of the EU and a free country again."

Of those voting Ukip, 57% said they were doing it because they liked the party. 34% said they were doing so because they liked Carswell, and 9% were doing so as a protest vote.

Immigration was Ukip voters main reason for choosing the party, with 47% describing it as their main concern. The EU accounted for 13%, with cost of living, jobs and health all accounting for less than 10%.

"There is a massive appetite out there for change."

According to the poll of 700 voters, Labour were on 13%, and the Lib Dems had 2%.

Of those that identified themselves as Tory voters, 49% said they considered Mr Carswell to be a hero. Only 17% thought him a traitor with the remaining 35% saying that they didn’t know.

Mr Carswell defected from the Conservatives last week. He has warned that more Tory voters could defect over David Cameron's immigration policies.

David Cameron arrives in Brussels (AP)

Mr Cameron has dismissed Mr Carswell's decision as "bizarre" because he had promised a referendum on the UK's membership of the EU by the end of 2017.

His plan to renegotiate the UK's relationship with Brussels was given a major boost by the new president of the European Council.

Donald Tusk, who will give up his job as Polish prime minister to take the role, singled out the UK's agenda as an area where he wants to make progress.

He said he "could not imagine" the EU without Britain as a member - insisting it would be possible to "reach an agreement" on issues such as freedom of movement of labour.

At a press conference after his appointment was finalised by fellow European leaders in Brussels, Mr Tusk said he wanted to "emphasise that the EU, and me personally, will take on the concerns voiced by the UK".

The strong words from Mr Tusk - who described the prospect of a British exit as a "dark scenario" - suggests he could be an important ally.

According to another translation the president-elect - who was unanimously backed by EU leaders - also said: "Many of the suggestions put forward for EU reform are sensible, we can work together to eliminate any welfare abuse by EU migrants."

Speaking to journalists as he left the EU summit in Brussels, Mr Cameron said: "I'm delighted obviously with what Donald Tusk has said about the importance of reform in the EU and addressing the concern that Britain has in the EU.