Douglas Carswell has denied suggestions he stabbed David Cameron in the back by defecting to Ukip.
He told ITV News' Libby Wiener he had nothing against "nice guy" David Cameron, but had to leave the Conservatives because the Prime Minister was "not serious about change".
He questioned what the difference would be if Ed Miliband's "gang replaced the current gang" in Number 10.
George Osborne has labelled the defection of Douglas Carswell to Ukip as "regrettable and counter-productive".
Speaking in Brighton today, the Chancellor said that the best way to secure a referendum on Britain's membership of the European Union was to have a Conservative government after the next election.
"That's the choice people are going to face, whether it's at the by-election in Clacton or at the general election next year," Mr Osborne said.
Nigel Farage, the Ukip leader, and the party's new candidate for Clacton have been campaigning on the streets of the seaside town this morning.
Douglas Carswell will contest the seat for the eurosceptic party after defecting from the Conservatives yesterday, triggering a by-election for the constituency.
Nigel Farage has reiterated more Conservative and Labour MPs are set to defect to Ukip following Douglas Carswell shock move from the Tories.
While on the campaign trail with Mr Carswell in Clacton this morning, Mr Farage said he expected more to jump ship if the Tory defector wins the by-election.
Mr Farage said, "Let's see what happens in this by-election, but if Douglas wins this by-election there'll be others - not just in the Conservatives but on the Labour backbenches too".
Conservative grandee John Redwood has dismissed the "so-called" eight Tory MPs allegedly considering defection to Ukip as "figments of Ukip's imagination".
"Dream on Ukip," the eurosceptic MP for Wokingham and former Wales Secretary told Radio 4's Today programme.
"I treasure the words of Mr Carswell which he was speaking yesterday. He said that we need to deliver an in-out referendum, he said it would only happen if David Cameron was prime minister," Mr Redwood said.
"He said we must do nothing to make the prospect of a referendum less likely. He was super-loyal until yesterday."
Ukip's general election candidate for Clacton has vowed to fight Douglas Carswell for the party's nomination in the upcoming by-election.
Roger Lord said he would "absolutely" fight for the nomination. "I have been assured I will get a fair hearing," he told Radio 4's Today programme.
Asked whether he would step aside to make way for Mr Carswell, Mr Lord replied, "We are not a party that stands down. We don't bend, we don't break. We fight."
Mr Lord also accused Mr Carswell of jumping ship from the Conservatives because the water was "around his ankles".
Nigel Farage has hinted that more MPs could follow Douglas Carswell by defecting to his party before the election.
The Ukip leader said politicians among the Conservative and Labour ranks "feel strongly" on the issues the party stands for.
"I don't think anybody will say that Douglas Carswell coming to Ukip is a one-off.
"There are many other people out there that are making up that calculation now," he added.
Douglas Carswell will return to his Clacton constituency today flanked by Ukip leader Nigel Farage as the pair plan a completely unexpected by-election campaign.
They are due to visit the seat after Mr Carswell's bombshell decision to switch parties and quit the Commons to re-stand under the Ukip banner.
The date for the by-election is yet to be set but is likely to be held within weeks. Parliamentary rules require an election between 21 and 27 days after a writ is moved to fill the vacancy.
A disgruntled UKIP candidate has spoken out after party leaders passed over him to back defected Tory MP Douglas Carswell instead.
Mr Carswell, the MP for Clacton, sparked a by-election after defecting from the Tories to UKIP.
And despite already selecting Roger Lord to fight the seat in next year's General Election, UKIP has announced it will be backing Mr Carswell in the pending by-election.
Speaking to BBC Essex, he said:
It is an enormous discourtesy, for anybody really, just to announce that and say that.
I think the last time I saw him, I said I would be prepared to give him a reference come next May if he found himself unemployed, which I am pretty sure he would be.
Perhaps he is jumping ship to try and get in front of all the other Conservative MPs who are going to find themselves in the unemployment queue come next May.
A UKIP spokeswoman said by-election candidates were selected differently to General Election candidates, and said she hoped he would "understand" the decision.
Prime Minister David Cameron has described Tory MP Douglas Carswell's defection to UKIP as "deeply regrettable" and "self-defeating".