Hastings MP Michael Foster last night helped defeat Tory opposition to plans to give unmarried and gay couples the right to adopt.

Mr Foster, the father of two adopted children himself, said opposing the move would leave hundreds of vulnerable youngsters stuck in residential care.

Tory leader Iain Duncan Smith imposed a three-line whip for his MPs to reject the Government proposal, part of the Adoption and Children Bill.

But Mr Foster urged MPs to examine their consciences before they voted, and it eventually won through with a 199 majority.

The Labour MP admitted "stereotype" married adoptive parents might provide the most stable home.

But, he said: "There are young people, many with disability and other challenges, that are not easily adoptable in terms of the stereotype husband-and-wife family "What I ask those who oppose this humanitarian piece of legislation is to search their conscience as to the reasons they oppose it.

"Do they in all honesty believe that the damage to a child in being brought up in what is still today a non-orthodox family is more damaging than being brought up in residential care?"

Horsham MP and former shadow foreign secretary Francis Maude was one of eight senior Tories who defied the three line whip to vote in favour of the proposals.

He was joined in the revolt by his close colleague Michael Portillo, whose challenge he backed in last year's Tory leadership contest.

A further six shadow cabinet ministers - including Arundel and South Downs' Howard Flight - were among the 35 Tory MPs who did not register a vote.

Other Tories who did not vote included Mid Sussex's Nicholas Soames, Bognor and Littlehampton's Nick Gibb and Chichester's Andrew Tyrie.

The seniority of the rebel MPs fuelled speculation of a leadership bid against the increasingly beleaguered Mr Duncan Smith.

The most damaging intervention came from Mr Portillo, whose leadership bid was run by Mr Maude - a leading Tory moderniser in charge of the CChange think-tank.

Throwing Mr Duncan Smith's conference speech that Britain had moved on in the past 20 years back at him, he asked why Tories had been put on a three-line whip for the vote.

East Worthing and Shoreham MP Tim Loughton, shadow health minister, was left to defend his leader in the Commons.

He said he believed there was no "middle way" and the Tories must resist adoption by unmarried and gay couples.

He said the leadership's view was motivated by the desire to provide the most stable future possible for children being adopted. Married couples were likely to stay together longer than unmarried couples.

The remaining Sussex Tory MPs - Eastborne's Nigel Waterson, Wealden's Charles Hendry, Bexhill and Battle's Gregory Barker and Worthing West's Peter Bottomley - voted with Mr Duncan Smith.

Mr Waterson said today: "I think most people would agree that adoption by homosexual couples is not ideal.

"I also think most people would agree that ideal adopters are married couples because children hoping for adoption have had enough instability in their lives already."