A member of the European Parliament told ITV News no one in Strasbourg ever asks for paperwork in relation to his allowances and expenses.
Ukip leader Nigel Farage said he is the victim of a "smear", after a newspaper claimed that he faces an investigation into his allowances.
Nick Clegg is hoping that there are votes to pick up in being the clearest voice on the pro-Europe side of the debate.
Ukip leader has refused to defend claiming a an MEP's monthly allowance of £3,580 because he says he wants the system abolished.
– Ukip leader Nigel Farage
All MEPs are given a fixed allowance of £3,580 per month.
They do not have to provide receipts for any of that expenditure, but there is a list that gives suggestions of what the money might be spent on.
It is not for me to defend this system: after all, I want it abolished. Ever since 1999, I have expressly stated that Ukip MEPs will use the wherewithal provided by the EU Parliament to campaign for Britain’s withdrawal from the European Union.
Writing in the Independent, he said that reports which used the word 'expenses' were a "deliberate and cynical attempt to conflate the anger over MPs expenses with the way that MEPs work".
Nigel Farage has criticised The Times after the newspaper claimed the Ukip leader was receiving EU cash to run his constituency office. Mr Farage told ITV News: "It's a classic case of me being singled out and treated differently to every other MEP".
The UK's election watchdog is writing to Ukip asking for "clarification" about the rent-free office at the centre of a row over Nigel Farage's use of Brussels' allowances.
The Electoral Commission said it wanted to find out if the rent-free arrangement should have been declared as a donation.
– Spokeswoman, Electoral Commission
We are writing to the party to just ask for clarification around this office that has come to light.
We just want to find out if anything needs to be reported that perhaps has not been.
Ukip leader Mr Farage has defended his use of MEPs' allowances and claimed he is the victim of a "political smear" following allegations about the money used to fund his constituency office.
The Times has responded to reports of Ukip leader Nigel Farage considering handing his expenses for independent scrutiny, after the newspaper claimed that he faces an investigation into £60,000 of "missing" MEP expenses. A spokesman for The Times said:
The Times welcomes Mr Farage's commitment today to open up his books to an independent auditor.
As our story states, the reporting was based on Mr Farage's own transparency reports.
A Ukip office manager who was a source for a Times article about Nigel Farage's expenses has accused the newspaper of "distorting" the information he gave them to "smear" the party.
David Samuel-Camps said the article incorrectly stated that running costs of Farage's office near Bognor Regis were £3,000 per year, after Samuel-Camps had told the paper the cost was £8,400 a year.
"I was completely honest in my answers and resent the fact that those answers have been completely distorted," Samuel-Camps wrote.
He added that Farage's office was "nowhere near Bognor Regis", and was in fact "on the outskirts of Littlehampton".
The Times said the reporting in the story was "based on Mr Farage's own transparency reports".
Nigel Farage said he is taking legal advice over what he called "outrageous and politically motivated" newspaper claims that he faces an investigation into £60,000 of "missing" MEP expenses.
"I have been accused, on the front page of the Times, of siphoning off EU money into the Cayman Islands. I am taking legal advice, I think this is completely and utterly outrageous," the Ukip leader told the BBC's Today programme.
The newspaper refers to Farage's use of a monthly allowance of £3,580 given to all MEPs.
"We don't want these allowances. We don't want MEPs costing the taxpayer all this money," he said.
Farage said MEPs were given a "a list as long as your arm" specifying what the money could legitimately be spent on, including "hotel bills, restaurant bills and subscriptions to websites".
"What we're seeing from The Times, not that I'm surprised, is another politically motivated attack from the establishment newspaper," Farage said.
Nigel Farage is reportedly facing an investigation into tens of thousands of pounds worth of 'missing' European Union expenses allegedly paid into his personal bank account.
According to the Times, Mr Farage has received around £15,500 per year since 2009 to pay for upkeep of his constituency office in Bognor Regis.
But the newspaper claims that the office - a converted grain store near Bognor Regis - was given for free to the party leader by Ukip supporters 15 years ago.
Once utilities and other non-rental costs are factored in, the Times estimates that around £12,000 a year is left unexplained.
A Ukip spokesman responded: “Nigel Farage is confident that he has abided by European parliamentary rules at all times when spending allowances.”
Nigel Farage has said he does not think Maria Miller resigning as Culture Secretary is "enough" and it is time voters were given the right to sack MPs who have stepped out of line.
The UKIP leader also rejected any suggestion that his own party had been abusing the expenses system in the European Parliament by using the money for eurosceptic campaigns.