Former senior Ukip MEP Amjad Bashir has defected to the Tories - but Nigel Farage’s party said it had suspended him over “grave” allegations of impropriety.
Prime Minister David Cameron told the Telegraph he was “absolutely delighted” at the Yorkshire and Humber MEP’s decision.
News of the defection emerged shortly after Ukip suspended the MEP, who was the party’s communities spokesman, over allegations including “unanswered financial and employment questions”.
Mr Bashir, who owned restaurants in Bradford, dismissed Ukip’s move as a “desperate attempt” to spoil the news of his decision to join the Conservatives.
Ukip said it had suspended Mr Bashir shortly before news of his decision to join the Tories emerged, and Mr Farage said the party had become “increasingly alarmed” about allegations of impropriety.
Mr Bashir dismissed his former party’s move as a “desperate attempt” to smear him to distract from the news of his decision to join the Conservatives and insisted there was “not a shred of truth” to the claims.
But Mr Farage told BBC 1’s Andrew Marr Show: “We have been increasingly alarmed by Mr Bashir’s behaviour over the last few months.”
He claimed the MEP “didn’t tell us the truth” about the alleged employment of illegal immigrants in his restaurant business and there are “some big open questions in Brussels about money”.
There were also claims of interference in candidate selection in Keighley, West Yorkshire and links with “political extremists” from Pakistan.
He warned Mr Cameron “caveat emptor” - buyer beware.
Mr Farage said: “The final straw on Friday, (was) the hustings meeting that took place in West Yorkshire where gerrymandering appears to have taken place.”
When Mr Bashir’s denials were put to him Mr Farage added: “He can deny that, but I tell you what he can’t deny and that’s his continuing association with political extremists from Pakistan despite us saying please, please, keep away.
“Whichever way we look at this, he had reached the end of the road with us, he knew that.
“My only surprise, and my genuine surprise, is that the Conservative Party have accepted him. Caveat emptor.”
The Ukip leader said last year MEPs had been “begging me to get rid of Amjad Bashir back in October and November of last year and I chose to take the tolerant approach and I was wrong”.
A Ukip spokesman said: “The UK Independence Party has a zero-tolerance policy and takes the matters at hand extremely seriously.
“The allegations against Mr Bashir are of a grave nature and we will be forwarding our evidence obtained so far to the police.
“Ukip will not tolerate anyone abusing their positions in the party, as we have a firm commitment to differing ourselves from the existing political classes. As a result, Mr Bashir’s involvement with the party was suspended today with immediate effect pending further investigations.”
But Mr Bashir said: “On Friday I met David Cameron and applied to join the Conservative Party.
“It is clear Ukip’s action today is a desperate attempt to spoil this and is without any foundation.
“The issues raised in my notice of suspension are historic and well-known to the party. Indeed, on one of them, Nigel Farage has publicly defended me over it.”
The coup is a major boost for the Prime Minister, who has suffered the defection of two MPs to Ukip and has seen the Eurosceptic party eat into Tory support.
Mr Cameron told The Telegraph during a meeting with Mr Bashir that he understood why voters had been tempted to Ukip.
“I understand why some people have drifted away to Ukip,” Mr Cameron said. “I want to genuinely win those people back by saying look, we are the only party that can offer the strong immigration control this country needs; we are the only party that can deliver that referendum that the British people deserve.
“And crucially, this general election is not a by-election, it’s not a beauty contest, it is not a chance to send a message or make a statement, it is about choosing a government of the United Kingdom.”
Mr Cameron said: “I’m absolutely delighted that Amjad has decided to leave Ukip and join the Conservative Party.”
Mr Bashir, who is a Muslim from a Pakistani background, had an “inspiring” story, Mr Cameron said.
He added: “It’s another sign that in this great country of ours you can come to Britain without very much and you can be a member of the European Parliament, an MP, sit in the Cabinet.”
Mr Bashir told The Telegraph that Ukip had become a “party of ruthless self-interest”, was “pretty amateur” and had a “ridiculous” lack of policies.
He said the party - which has seen its opinion poll rating soar and topped the national poll in last year’s European elections - was “delusional” about its chances of winning seats in May.
He said: “After almost three years as a party member, I realise that Ukip is more concerned with furthering its own interests as a political party than delivering for the British people.
“I’ve seen Ukip both at home and abroad, and I’m sorry to say they’re pretty amateur. In the European Parliament, some of their MEPs think it’s acceptable to shout and fool around.”
He added: “They think they’ll sweep up dozens of seats in May, but that’s delusional. What they are in very real danger of doing, however, is making a big enough dent in the Conservative vote to let Labour in.”
Labour’s Jon Trickett, the shadow minister without portfolio, said: “This latest defection shows more than ever there is a revolving door between Ukip and the Tories.
“Conservative MPs defect to Ukip and Ukip MEPs flee back the other way when Nigel Farage says they have questions to answer.
“Ukip and Tories share policies as well as people - both parties want to increase NHS privatisation and cut taxes for those at the very top. All that’s clear is that neither party can be trusted to stand up for hardworking families.”