UKIP’S only MP has backed a rival EU-out campaign after labelling the party leader’s preferred group as a “donkey”.

Clacton MP Douglas Carswell is supporting the ‘rival’ cross-party Vote Leave campaign for Britain to exit the European Union.

He said it is the clear front runner to be designated the official “out” campaign in the forthcoming referendum.

The move puts him at odds with party leader Nigel Farage who has pledged to work “hand in hand” with the Leave EU campaign, launched by wealthy Ukip backer Arron Banks.

The group that wins the official designation will benefit from up to £600,000 of public funding, as well as higher spending limits, campaign broadcasts and free mail shots.

“There are two campaigns vying to be the official campaign,” Mr Carswell told the Gazette.

“It was at one time a two-horse race, but now it’s a one-horse race.

“I want to back the thoroughbred, not the donkey.”

Mr Carswell said his choice to back Vote Leave is not against party policy and that the party’s National Executive Committee reaffirmed on Monday that it would work with all groups who stand a chance of getting the official designation from the Electoral Commission.

“It’s simply not party policy to say we’ll work with one specific campaign,” he said.

“Everything I’m doing is 100 per cent in line with party policy.

“Just looking at this from the point of view of mathematics – I was the only Ukip candidate at the last election to get elected and even I only got 44 per cent of the vote.

“I couldn’t get a majority in favour of leaving the EU if I did this just as Ukip.

“That’s why I’m working with Bernard Jenkin and people from all parties to tell people we would be better off out.

“As a country we face enormous economic and technological challenges. The EU, which was founded half a century ago, just doesn’t have control over those changes.

“We need to vote to take back control.”

Mr Carswell said it would be bad for Ukip and the ‘out’ campaign if Ukip cut itself off from the group that was most likely to get the official designation.

He has already clashed with Mr Farage over the issue, following which the party leader accused Mr Carswell of “residual loyalties” towards the Conservatives.

But he has now moved to play down rifts within the out campaign, insisting he supported both the Leave EU and Vote Leave.

Mr Farage argued the two organisations were "complementary", with one targeting the grass roots and the other dominated by Westminster figures.

“I am not in any campaign. I am the leader of Ukip,” Mr Farage said. “There are two groups who have set themselves up to be umbrellas, but they are both completely different.”

Asked why Ukip's sole MP Douglas Carswell was in Vote Leave but not Leave EU, Mr Farage said: “He is in Westminster and he is with a group of people.”