Farage said candidates that he would “rather not have had” could be standing in the elections because UKIP lacked the means to fully vet them.
His comments came after it emerged that a candidate had been thrown out of the party when it was discovered that she used to be a BNP member. Susan Bowen, a retired sheep farmer from Boscastle in north Cornwall, had been selected to stand in the Tintagel ward on 2 May.
She was once a BNP activist and spoke at a far-right meeting in 2010, footage from which is on YouTube. Farage told the BBC’s World at One programme that the party had to rely on candidates being honest about any criminal convictions and other issues.
He said there may be “one or two” council candidates that UKIP would not be happy with, but said it was not possible for the party to vet all 1,700 in time.
“When it comes to the general election and the European elections, we have put in place a very rigorous testing procedure – testing people’s knowledge, their ability with media – you know, full credit checks, police checks and all the rest of it,” said Farage.
“I’ll be honest with you, we don’t have the party apparatus in a very short space of time to fully vet 1,700 people.
“We have made people sign declaration forms, expressing the fact that they’ve never been part of political parties that we consider to be wholly undesirable with some exceptions, including a former NF Candidate standing in Kent.
“By that I mean the BNP & NF. And, you know, we ask people if there is a problem with a criminal record or whatever else it may be, please tell us.
“I have no doubt that among those 1,700 one or two people will have slipped through the net that we’d rather not have had.”
Political analysts have predicted that Ukip is set to make the “most serious fourth party incursion in English politics” since the second world war – with the Tories as the main victims.
John Curtice, professor of politics at Strathclyde University, said on Wednesday that around 16% of Tory supporters at the last election say they would now vote Ukip. This compares with 8% for the Liberal Democrats and 4% for Labour.
A UKIP spokesman said: “We’ve got the honesty to admit we’re not perfect. We don’t have absolutely 20:20 vision on all our candidates. We ask people questions.
“We like to take people’s words on it. However, sometimes we get burnt. But when we do get burnt we act.”
“However we have been highly critical of other political parties, which with hindsight is regrettable and rather stupid”