Ukip are a party for "decent" supporters of the BNP who worry about being "swamped" by immigrants, the deputy chairman of the party has said.
Former Tory MP Neil Hamilton said "a lot of decent people" who had previously voted for the BNP were now turning to Ukip instead.
"They feel their communities are being swamped by immigrants from outside, whether they are from Eastern Europe or from other parts of the world," he told the BBC.
"Now those people, the decent supporters of the BNP, from the last election, who weren't true BNP supporters at all, I am sure that quite a few of them are voting for a respectable alternative, which is Ukip," he added.
Hamilton's comments were reinforced by BNP leader Nick Griffin, who accused the Eurosceptic party of stealing their support.
"They [Ukip] are using all of our rhetoric, they are using our slogans, they are recycling our posters and people like it," he told Pienaar's Politics.
Griffin has previously attacked the party for using the slogan "Love Britain, Vote Ukip" following his own party's use of "Love Britain, Vote BNP.
Hamilton's comments come at an unfortunate time for the party, as it tries to fight off accusations of being "the BNP in blazers".
The party was forced onto the defensive last week after a Ukip council candidate was found to have tweeted that Lenny Henry should go back to a "black country".
William Henwood later defended his tweet, telling the BBC that "I think if black people come to this country and don't like mixing with white people why are they here? If he (Henry) wants a lot of blacks around go and live in a black country."
A Ukip spokesperson distanced the party from Henwood, but blamed other parties for trying to distract the public.
"Any breach of our rules will be duly investigated and action will be taken," they said.
"However one has to question why the other parties are spending hours behaving like secret police and trawling through the social media of Ukip candidates who are everyday men and women, rather than actually doing politics.
"Perhaps if they did they would be better able to tackle us on policy, rather than having to rely on smear campaigns to try to undermine Ukip's increasing popularity."
Attacks on Ukip have so far failed to dent their support. A poll over the weekend found that they had moved into the lead in the run-up to the European elections for the first time.
According to Yougov, the party now has the support of 31% of voters in the elections, with Labour on 28% and the Conservatives on just 19%.
The pollsters failed to find any voters who now plan to vote for the BNP.