He said David Cameron's election campaign was based on scaremongering – and claimed that wheeling out former leader Sir John Major was utterly pointless.

Carswell, who defected from the Tories to UKIP last year and is fighting for re-election in Clacton, Essex, told BuzzFeed News: "It's based on smear and jeer and it tells you about their values and their cynical manipulative politics.

"The party that produced Margaret Thatcher is reduced to trying to frighten people to vote for it. That's what it's come to."

He was speaking from Rochester, in Kent, where he was campaigning on behalf of his fellow defector, Mark Reckless.

As national polls continue to flatline, the Tories have stepped up their attacks on Labour by warning that Ed Miliband will end up sharing power with the left-wing SNP in a "coalition of chaos".

On Monday former prime minister John Major made a speech underlining this, saying Scottish nationalists would make "merry hell" with Labour.

"Last time John Major was wheeled out by the Conservative party was 1997," Carswell said. "I'm not sure it worked out too well then.

"Many of the people in Rochester and Clacton – they voted Thatcher in the 1980s and Tony Blair in the 1990s – they've given up on the lot. What makes people think wheeling out Blair and Major as the big corporate parties have done will win them back?"