Nigel Farage has said he is taking legal advice over “outrageous” allegations concerning his use of EU expenses.
Ukip faces the prospect of financial investigation amid allegations that its leader is responsible for more than £50,000 of “missing” European Union funding that was paid directly into his personal bank account.
But in an interview on BBC Radio 4's Today programme, Mr Farage rejected claims that he may have abused EU expenses in an article for The Times as a "politically motivated attack".
He said: "This whole story and even the line of questioning here is simply wrong."
"I've been here since 1999 and I've said since day one that I would use the money and the wherewithal provided by the European Union to fight against Britain's membership of the European Union, but to do so within the rules of the parliament.
"And what we are seeing here from The Times - I mean not that I'm surprised because we have been expecting this - we are seeing yet another politically motivated attack from what is the establishment newspaper."
He added: "I am taking legal advice; I think this is completely and utterly outrageous."
Mr Farage is understood to have received £15,500 a year from Brussels since 2009 designated to the upkeep of his constituency office, a small farmyard building in Lyminster, West Sussex.
However a former political assistant to the party says the office was donated rent-free to Mr Farage by party supporters 15 years ago. Utilities and other non-rental costs amount to no more than £3,000 a year, according to the former office manager, leaving about £12,000 a year unexplained.
The £15,000 a year paid for out of EU allowances since 2009 is an entitlement to all MEPs with no requirement for them to justify their spending. But a former manager at the constituency office told The Times that the correct figure was closer to £3,000 a year, a claim reportedly disputed by Ukip.
David Samuel-Camps, 69, who worked as political assistant to Mr Farage between 2002 and 2010, was responsible for keeping the accounts for the office since about 2005. “Every month I’d contact Nigel one way or the other and say can you send me a cheque, you know the monthly cheque for however much it was,” he told The Times. “He would send me a cheque, which I recall was a personal cheque, which I would then put into our office account in Arundel. And then I would draw on that, as and when, for paying invoices.”
Mr Farage told the newspaper that he transferred £1,000 a month to run the office, without specifying what costs this covered. A Ukip spokesman did not return calls last night.