Messrs Shaw and Ng don't hold out much hope that the department will recognise their Canadian marriage licence either, and are prepared to wait for a legal ruling Mr Shaw expects will take 'up to three years', most likely from the High Court. 'We're hopeful about the outcome of a judicial review on the validity of our marriage contracted in Canada, because everywhere in the statutes of Hong Kong you see recognition of overseas marriage,' says Mr Shaw, who has a Master of Laws from the University of Hong Kong.

'I don't think there are sufficient grounds for the government to exclude overseas marriage between members of the same sex ... and I don't think a court will want to overturn the spirit [of recognising overseas marriages] contained in our statutes.'

Mr Shaw does not see his and Mr Ng's fight for recognition of their marriage as an issue of concern to 'political forces' at play in Hong Kong, although it will likely be closely watched by gays on the mainland. 'Hong Kong has the advantage of the Basic Law, and the Bill of Rights as the human rights guarantee for the people of Hong Kong and ... we should take advantage of that,' he says.

Mr Shaw wants Hong Kong to try to reach a consensus on same-sex marriage because 'if it is going to be legalised, I think it is important the people ... accept that same-sex couples should have the same protections as opposite-sex couples.

'The current heated debate in places like the US is a good thing - by debating, people get to know more of where they stand and where other people stand.'

The debate in the US has been swirling since late last year, when the Massachusetts Supreme Judicial Court ruled on November 18 that not allowing same-sex couples to marry was a violation of anti-discrimination laws, and gave the legislature until May 17 to do something about it.

The Massachusetts legislature did approve an amendment to the state constitution in March that states marriage is between one man and one woman, but the amendment is subject to two more votes, and if passed would not come into effect until late 2006.

Meanwhile, the US Supreme Court last Friday declined to become involved in an action brought by conservative groups trying to block gay marriage in Massachusetts, sending the case back to the US First Circuit Court of Appeals in Boston, which will hear legal arguments on June 7.

'The battle over same-sex marriage is far from over - in fact, it is only just beginning,' Mathew Staver of Liberty Counsel, which will represent gay marriage opponents in the appeal, said in Washington.

US President George W. Bush weighed in on Monday with a fresh call for a constitutional amendment banning same-sex marriages. 'The need for that amendment is still urgent, and I repeat that call today.' That call was contained in his address to mark the 50th anniversary of the civil rights movement in the US.

'We see this as the next battle against discrimination, and it is not surprising that the same arguments used by opponents of racial equality are being used today. Then, as now, those arguments are just as spurious,' says Liz Whitelam, gay and lesbian rights activist for Amnesty International in Hong Kong.

John Kerry, the Democrat challenger to Mr Bush in presidential elections set for November, is a US Senator from Massachusetts. Mr Kerry said in February he had no objection to same-sex couples being granted civil unions that would safeguard the 'fundamental rights of gay and lesbian couples, from inheritance to health benefits', but he was opposed to calling it 'marriage'.

Across the US, debate on gay marriage is divided between those who back the unions on civil rights grounds and those who often cite religious reasons in opposition.

Fundamental to the debate is the Massachusetts ruling: 'Barring an individual from the protections, benefits and obligations of civil marriage solely because that person would marry a person of the same sex violates the Massachusetts Constitution.'

In Britain, the House of Lords is debating a civil partnership registration bill - put forward late last year by the Blair government and with the support of the opposition Conservatives - that will confer on same-sex couples all the rights and responsibilities of opposite-sex marriage. That bill is expected to be gazetted early next year.

The British government estimates that even under a high take-up scenario matching the proportion of marriages in the heterosexual population, about 33 per cent of gay and lesbian couples will register partnerships. Based on the experience of similar arrangements in the EU, the rate of civil partnership registration will likely be one-tenth the heterosexual marriage rate - or 3.3 per cent.

The only openly gay member of the House of Lords, Baron Waheed Alli of Norbury, 40, who has been with his partner for 23 years, said last month: 'I cannot tell the House what the Bill will mean to many gay men and women, in terms of the relief that at last we might find some kind of recognition by the state, and therefore society as a whole, for our relationships.'

Nine other countries in the EU have some provision for recognising those in committed same-sex partnerships. Belgium and the Netherlands provide for same-sex marriage, Sweden is considering a similar move, and Spain's new prime minister, Jose Luis Rodriguez Zapatero, says he will push for such a law in the predominately Catholic country.

Some governments, however, are following the Bush administration's line in seeking to entrench marriage as a solely heterosexual union. Australian Prime Minister John Howard, facing a close election later this year, says he wants to amend the Marriage Act (1961) to ban gay marriages.

Taiwan President Chen Shui-bian's highly public attempt last December to push a Human Rights Bill that would include recognition of same-sex marriage stalled in cabinet and was shelved ahead of the elections, but has yet to re-emerge despite Mr Chen's re-election.

A significant issue for Hong Kong is whether the recognition of the rights of same-sex couples will harm its economic development, says Mr Shaw.

His non-governmental group, Civil Rights for Sexual Diversities, has heard of numerous cases where foreign gay couples face enormous obstacles when one member is posted to Hong Kong and cannot obtain a visa for his or her partner. None have sought to expose themselves to a court challenge.

A Canadian couple, married in Vancouver, was recently denied such a dependant's visa on the grounds that gay marriages are not recognised in Hong Kong. 'The existing immigration policy on admission of spouses as a dependant in Hong Kong is based on monogamy and the concept of a married couple consisting of one man and one woman,' a spokeswoman for the Immigration Department says.

Other gay couples, where one is not a Hong Kong permanent resident, have set up registered companies to circumvent the department's stance.