An MP who spearheaded reform of the adoption system has spoken out against moves to allow gay or unmarried couples to adopt.

An amendment to the Adoption and Children Bill, freeing up the process to same-sex and unmarried couples, was passed in a free vote in the Commons by 288 votes to 133, a majority of 155.

But Conservative Party chairman David Davis said these couples did not offer the stability needed for children "badly damaged" by years in care.

The Haltemprice and Howden MP said many children had been in and out of care and foster homes and were in need of stability, but he argued unmarried couples were more likely to break up than married ones.

Mr Davis also dismissed the idea of gay couples adopting, saying: "I don't want to experiment with children.

"They need the right sort of upbringing and I believe that means a mother and a father."

He added: "What we are talking about is kids with really tough lives, in and out of care homes, in and out of foster homes, badly damaged.

"They do not need the additional stress of being placed with a couple where the survival rate of the relationship is already low."

Mr Davis has championed the new legislation, which relaxes restrictions on who can adopt.

At Thursday's meeting, the MP branded current restrictions as "silly" - such as not allowing a white couple to adopt a black child.

He added: "There may well be unmarried couples who will make wonderful parents, but you cannot tell."

But Mr Davis, who was brought up in a one-parent family, said he had no problem with individuals adopting.

The amendment was supported by Health Secretary Alan Milburn on Thursday night but a Conservative clause has been tabled to exclude gay couples.