Nigel Farage has risked accusations of racism after saying he is "proud" to have formed an official alliance with far-right politicians in the European parliament.
Ukip have joined forces with members of the Sweden Democrats party and a former member of the French National Front.
Farage had promised not to form any alliance with far right parties in Europe.
However, the Sweden Democrats were founded as a white supremacist organisation. One prominent figure in the party was a former member of the Waffen SS.
In 1996, their leader placed a ban on the wearing of uniforms, in order to stop members of the party from dressing as Nazi officers during meetings.
A leading member of the party was forced to stand down last year after it was revealed she had posted a comment saying that asylum seekers should starve to death.
Ukip have also admitted former National Front MEP Joëlle Bergeron to their Europe of Freedom and Democracy group. Bergeron resigned from the far-right party just two days after being elected.
Farage said he was "proud" of his new alliance.
"I am very proud to have formed this group with other MEPs and we undertake to be the people’s voice," he said.
The two members of the Sweden Democrats party yesterday issued a statement in which they distanced themselves from their parties extreme past.
"We acknowledge and learn from our mistakes", they said.
"The worst of these mistakes was that the party didn't distance itself from radical youths with subcultural looks and that these were allowed to participate in some of the party demonstrations."
Ukip yesterday came under attack for associating with the "dregs of the far right".
"Regardless of your views on Europe, it is hard to see how British MEPs hanging around the European parliament with the dregs of the far right is going to be of any benefit to British jobs and growth," a senior Lib Dem source told the Guardian.