Labour has called on Conservative Welsh Secretary David Jones to apologise for saying that same-sex parents would not be able to provide a “warm and safe environment” for children.

On Friday evening, a spokesman for the prime minister commented by saying David Cameron rejects Mr Jones’ claims about children in same-sex families and that he is in favour of same-sex adoption.

“The prime minister believes gay families can provide warm and safe environment for raising children,” the spokesman said.

Yesterday, Mr Jones told ITV Wales: “I regard marriage as an institution that has developed over many centuries, essentially for the provision of a warm and safe environment for the upbringing of children, which is clearly something that two same-sex partners can’t do.

“Which is not to say that I’m in any sense opposed to stable and committed same-sex partnerships.”

The senior Tory cabinet minister was explaining his decision to vote against the Marriage (Same Sex Couples Bill) – along with 135 other Tory MPs in last week’s Commons vote.

However, his comments were denounced on Friday by equality campaigners and by his political rivals.

Labour’s shadow equalities minister Kate Green branded Mr Jones’ remarks “hugely insulting, offensive and wrong”.

Shadow Welsh secretary Owen Smith claimed the comments proved that the “nasty party is alive and well under David Cameron”.

On Friday afternoon, Mr Jones released a statement saying: “I made the point of stressing that I was fully supportive of committed same-sex relationships. I also strongly approve of civil partnerships.”

“I did not say in the interview that same-sex partners should not adopt children and that is not my view.”

Meanwhile Labour’s shadow immigration minister Chris Bryant has now written a letter to Mr Jones, asking him to withdraw his comments – or provide evidence for his claims.

Mr Bryant wrote:

Following your comments on last night’s ‘Face to Face’ programme broadcast by ITV Wales, I felt I had to write to you for clarification. As you are aware, in the interview you asserted that only a married heterosexual couple could provide a “safe and warm” environment in which to raise children and that a lesbian or gay couple could patently not do so.

The clear inference is that you believe that same-sex couples are somehow not to be trusted with children. I urge you as a matter of urgency either to publish any evidence you may have for this inflammatory claim or else to make a full and unconditional apology to the many same-sex couples who already have children and are raising them in perfectly safe, warm and loving environments.

If you are unable to provide any evidence, then I can only assume that your comment is the product of homophobic prejudice of the first order and it cannot be allowed to go unchallenged. People are entitled to their views on same-sex marriage, but to cast aspersions on same-sex couples’ ability to provide safety and security for children is profoundly irresponsible, especially considering the fact that many such couples provide foster and adoptive homes for the most difficult to place children. I hope you will reconsider.