Media reports indicate that a local authority has removed three non-white children from their foster parents because the couple are members of the anti-immigration UK Independence Party.
The couple from Yorkshire said they had been fostering children for seven years but have been told by social workers that they were not suitable because of UKIP's calls for curbs on immigration to Britain.
The woman, a qualified nursery nurse, told the Daily Telegraph newspaper that they had had the baby girl, boy and older girl for eight weeks when two officials came to question them about their reported membership of UKIP.
She said the social worker told her: "We would not have placed these children with you had we known you were members of UKIP because it wouldn't have been the right cultural match."
The woman said she asked what UKIP had to do with the decision, "then one of them said, 'Well, UKIP have got racist policies'. The implication was that we were racist."
The couple, whose identity has not been released to protect the children, said they had been "stigmatised and slandered".
The director of children's services at the local authority, Rotherham Metropolitan Borough Council, defended the move.
Joyce Thacker said three ethnic minority children had been placed with the couple as an emergency and it was never meant to be a long-term arrangement.
"These children are not UK children and we were not aware of the foster parents having strong political views. There are some strong views in the UKIP party and we have to think of the future of the children," Thacker told the BBC.
However, UKIP leader Nigel Farage said the situation was "appalling" and "disgraceful" and accused the council, which is run by the opposition Labour party, of bigotry.
He denied his party was racist, saying fostering decisions should be "colour-blind".
A Labour spokesman called for the council to undertake an urgent investigation into what happened, adding: "Membership of UKIP should not block parents from adopting children."
UKIP started life on the fringes of politics but has grown to become Britain's fourth largest party, attracting 3.1 percent of the vote in the 2010 election.
It has 12 members of the European Parliament and 31 local councillors, although it has yet to win any members of the House of Commons.
UKIP wants Britain to withdraw from the European Union and wants a five-year freeze on permanent immigration.