The Government will try to overturn a House of Lords vote, which would maintain the ban on unmarried and gay couples adopting children.

The Lords voted last night to keep the prohibition by a majority of 34 during the Adoption and Children Bill's report stage.

The defeat was a setback for ministers who want to get the Bill onto the statute book before the opening of Parliament's next session on November 13.

Afterwards social services minister Jacqui Smith said: "I am disappointed that the Lords have voted in favour of restricting potential adoptive parents to only married couples.

"The Commons overwhelmingly endorsed the need to widen the pool of potential adopters, ensuring that more children are adopted from care and placed with stable and loving families.

"The Government's aim has always been to ensure that more vulnerable children have the chance of family life that adoption can bring."

The Commons looks sure to reinstate the gay/unmarried couples provision before sending the Bill back to the upper chamber.

It is not immediately clear what the measure's fate would be should the Lords again defy the Commons' wishes.

The move to reject the plans was led by opposition spokesman Earl Howe, who argued that vulnerable children should be safeguarded. He said that marriage was the best way to ensure stability in the home.

Peers had a free vote in a large turnout, which included former Prime Minister Baroness Thatcher.