Nigel Farage is facing allegations over an expenses fraud probe worth thousands of pounds paid to him by the EU.
Questions were raised about what happened to money intended for running a party office called the Old Grain Store in Bognor Regis, West Sussex.
The Ukip leader said he was considering taking legal action over the claims made in The Times.
He said maintenance and bills at the property cost around £1,000 a month. According to the former manager of the office, the monthly bill is less than £250.
Under the terms of the General Expenditure Allowance, Farage received £15,500 a year to cover the costs. The focus will now fall upon what happened to nearly £60,000 unaccounted for, after payment of bills.
The body at the EU which investigates fraud has been sent a complaint about alleged missing thousands from expenses paid to Farage every year since at least 2009.
The former banker branded the allegations against him "outrageous, ridiculous and absurd" and claimed it was part of a plot "to nobble me." He vowed to "never speak to The Times again."
Farage denied the allegation by claiming the money was an allowance with which he was entitled to do what he liked. He said the claims were made by former party members with a grudge.
In a written statement, a Ukip spokesman said: "Nigel Farage is confident that he has abided by European parliamentary rules at all times when spending allowances."
The toxic issue of expenses comes ahead of local and EU elections next month, at which Ukip is eyeing big gains. That makes the prospect of a fraud probe over his own expenses awkward for Farage, whose high personal ratings are partly founded his image as 'anti-politics' politician who stands against 'politics as usual.'