Nigel Farage, the leader of the Ukip party in Britain, has promised to use money saved by quitting the European Union to inject extra cash into the NHS as he sought to limit the damage caused by a Ukip MEP defecting to the Tories and embarrassing comments from a senior party official.

Farage, who pledged an extra £3 billion a year for the health service, hit out at the party’s former communities spokesman Amjad Bashir after his defection to join David Cameron’s party.

Ukip said it had suspended Bashir shortly before news of his decision to join the Tories emerged, and Farage said the party had become “increasingly alarmed” about allegations of impropriety.

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 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 Cameron “caveat emptor” – buyer beware. When Bashir’s denials were put to him 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”. Bashir left his former party with a stinging parting shot, telling The Telegraph that Ukip had become a “party of ruthless self-interest”, was “pretty amateur” and had a “ridiculous” lack of policies.

Farage predicted that Ukip would win a “good number” of seats at the general election, adding that meant “more than three or four”. He said joining a formal coalition was “unlikely” adding “don’t think the lure of a ministerial car is the reason I got into politics”.

Ukip “couldn’t do any deal with Ed Miliband” unless he agreed to a referendum on Europe, while Farage said he would only support the Tories if they agreed to hold an early in/out vote under strict rules banning citizens from other EU countries participating. He added: “I want a guarantee that in this referendum the only people that can vote are British citizens because at the moment there are four million or so EU citizens living in Britain who I do not think should be allowed to vote in that referendum.”

Farage insisted Ukip was committed to a health service that was free at the point of delivery. But he said the service was struggling because of the “massive increase” in the country’s population. He called for measures to crack down on health tourism and said people studying for medical subjects should be exempt from tuition fees to reduce the NHS’s reliance on migrant workers.

He said: “We think the fact that health tourism is costing £2 billion a year is wrong and the fact that one in five new nurses being taken on have to come from abroad says to us ‘let’s make sure there are no tuition fees for people who are taking medical degrees. We want a National Health Service that is free at the point of delivery and funded through taxation. But the one thing nobody dares say is the reason we have an NHS crisis right now is because of a massive increase in the population in this country.”

He added: “We would promise an extra £3 billion a year for the National Health Service funded out of the fact that we will not be paying daily membership fees as members of the European Union.”

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