UKIP leader Nigel Farage admitted that a candidate pictured on the front page of a newspaper making the Nazi salute did "not look very pretty" ahead of Thursday's local elections.
Mr Farage, who said there had been "one or two teething problems" with the party's candidates, blamed UKIP's rapid growth for meaning some inappropriate people had slipped through the net.
He told BBC Radio 4's Today programme: "We have had, out of our 1,700 candidates, a handful who have embarrassed us, mostly because they simply haven't told us the truth.
"We are the only party in British politics who actually forbid former members of the BNP or extreme organisations from even becoming members of Ukip, let alone candidates and, in one or two cases, people haven't told us the truth.
"A huge amount of time and money has been spent on researching every single UKIP candidate standing in these elections. I would speculate if the same amount of scrutiny was put on the Labour and Conservative Party, they would find their own embarrassment."
More top news
David Cameron will promise to build 200,000 affordable new homes to transform young people from "generation rent to generation buy".
A vulnerable man who accused Leon Brittan of sexual abuse has claimed he was encouraged to make the allegations by campaigners.
Heavy downpours have triggered flash floods in Yorkshire.