Mr Howard said he "strongly" believed in the measures

He asked parliament to amend the law to specify that marriage must involve a man and a woman, and also to stop gay couples adopting foreign children.

At present, homosexual partners cannot marry. But some have done so overseas and asked Australia's courts to recognise their union.

The proposals were criticised by gay rights activists as "offensive".

Mr Howard said marriage should be defined as a "voluntarily entered-into union of a man and a woman to exclusion of all others".

"I believe in these measures - they wouldn't be coming forward if I didn't believe very strongly in them," he said.

Somali Cerise, a spokeswoman for Australia's Gay and Lesbian Rights Lobby, said she was angry and concerned by Mr Howard's move.

"He's saying our relationships aren't as valid as heterosexual relationships, that the love and care isn't the same. It's offensive and hurtful," she told BBC News Online.

What Howard is doing is borrowing a tactic from George Bush Somali Cerise, Gay and Lesbian Rights Lobby

While homosexuals have not been able to marry in Australia law, the proposed changes to the law would prevent same-sex couples marrying overseas and then applying to have their marriages recognised at home.

"Three Australian couples have recently got married in Canada, and are trying to get their unions recognised through the courts here," said Ms Cerise.

"Mr Howard is trying to pre-empt the court's decision."

Critics said Mr Howard's move was an attempt to split the Labor Party, which is thought to be divided on issues of gay rights.

But Labor frontbencher Nicola Roxon said: "Labor has made clear that we don't support gay marriage. We are not going to get hot under the collar about a piece of legislation which is just confirming the existing law."

The proposed changes must now pass the government-dominated lower house and then the Senate, where minor parties hold most of the power.

Superannuation benefits

In a related move that will be seen as a concession to gays and lesbians, Mr Howard announced on Thursday that people in a same-sex relationship would be recognised for the first time as financially dependent partners.

This means they will be able to get a partner's state-paid pension after their death.

Somali Cerise welcomed the move, but said it was long overdue.

Mr Howard said the change was not aimed exclusively at gay couples, pointing out that two elderly sisters living together in a financially interdependent relationship would also be covered.

Mr Howard's proposals will also prevent same-sex couples being able to adopt children overseas.

Adoptions in Australia are a state not federal matter. Mr Howard said he would like to impose a ban on gay couples adopting children, but added that the constitution did not give him the power to override state governments on the issue.