Downing Street has insisted the government will press ahead with the repeal of Section 28, which bans the promotion of homosexuality in schools.

But the Prime Minister's official spokesman, Alastair Campbell, did not say if ministers would push ahead with the clause's abolition if it was defeated a second time in the House of Lords.

Mr Campbell said: "It is back in the Commons, then it will go back to the Lords - then, see what happens.

"I will not hypothesise beyond that."

The government may have to do a deal with peers if the bill is rejected a second time or risk losing those parts of the Local Government Bill which contain plans to spread elected mayors across England and Wales.

More Labour peers on the way

Because the bill started in the Lords rather than the Commons, the government cannot use the Parliament Act to force it through.

Reports in Monday's Daily Mail newspaper suggest that the government will concede defeat on the controversial issue if peers reject it again.

And although the government is expected to announce a new tranche of Labour working peers this week it is unlikely to defeat the cross-party alliance against repeal.

Last week ministers suffered a further set-back on the issue when an amendment to the Learning and Skills Bill, bringing in new guidelines on sex education, intended to allay the fears of opponents of Clause 28 repeal, was also thrown out by the Upper House.