An investigation has been launched into the decision by social workers from Rotherham Metropolitan Borough Council to remove the three children – who are European migrants – after discovering the married couple were members of the anti-Europe party.
The children – a baby girl, a boy and an older girl all under 10 – stayed with the couple for eight weeks.
They are said to have been removed from the couple, who are in their late 50s and have not been identified, because of concerns about their "cultural and ethnic needs".
The couple have claimed social workers told them the Ukip party – which wants the UK to exit the European Union and backs tighter immigration rules – was "racist".
But yesterday the female carer said the children were encouraged to speak their own language and that steps had been taken to find an appropriate school to meet their religious needs.
The woman said: "We were actively encouraging these children to speak their own language and to teach us their language.
"We enjoyed singing one of their folk songs in their native language, and having been told of the religious denomination of these children we took steps to ensure that a school of their denomination was found."
Roger Stone, leader of the Labour-run authority, announced the investigation after mounting condemnation of the decision from political leaders.
He said: "We are going to investigate to make sure everything has been done professionally. We are looking to make sure all the correct procedures were carried out before the decision was made."
Tory Education Secretary Michael Gove said social workers had made "the wrong decision in the wrong way for the wrong reasons" and that he would be personally investigating and exploring steps to "deal with" the situation.
The politician, who was adopted as a child, accused Rotherham of sending out a "dreadful signal".
"We should not allow considerations of ethnic or cultural background to prevent children being placed with loving and stable families," he said.
Labour leader Ed Miliband called for an urgent investigation and said being a member of Ukip should not be a bar to adopting or fostering children.
Ukip leader Nigel Farage called for resignations over what he said was an "appalling" decision.
The Equality and Human Rights Commission said the decision may have breached the parents' right to freedom of political opinion.
Joyce Thacker, Rotherham council's strategic director of children and young people's services, said the decision to remove the children had been taken after consultation with lawyers.
Asked what the specific problem was with the couple being Ukip members, Thacker said: "We have to think about the clear statements on ending multiculturalism, for example.
"These children are from EU migrant backgrounds and Ukip has very clear statements on ending multiculturalism, not having that going forward, and I have to think about how sensitive I am being to those children."
She added that there was no issue about the quality of care the couple provided and said she would co-operate with any investigation into the council's decision.