In a High Court ruling, senior judge Mark Potter said giving legal recognition to gay marriages would "fail to recognise physical reality".

Sue Wilkinson, 52, and Celia Kitzinger, 49, who married in British Columbia in August 2003, lost their legal fight to have their union recognised in Britain.

The marriage of a man and a woman was different to a same-sex partnership, Potter ruled.

"The majority of people, or at least of governments ... regard marriage as an age-old institution, valued and valuable, respectable and respected, as a means not only of encouraging monogamy but also the procreation of children ... in a family unit in which both maternal and paternal influences are available," the judge said.

"Abiding single sex relationships are in no way inferior, nor does English law suggest that they are by according them recognition under the name of civil partnership."

New laws which came into effect last year gave same-sex couples legal status through "civil partnerships".

But unlike those in Belgium, the Netherlands, Spain and Canada, Britain's same-sex civil partnership is not a marriage.

Lawyers for the couple said their Canadian marriage should not be "downgraded" to what they considered the "lesser substitute" of a civil partnership.

The couple, who have been together for 16 years, claimed their marriage was valid under the European Convention of Human Rights. They spent their life savings to bring the legal challenge.

The couple said the judgement was "deeply disappointing" for themselves and for same-sex couples across the country and said it would one day be swept aside.

"Denying the validity of our marriage upholds discrimination and inequality," Wilkinson said. "This judgement will not stand the test of time."

Gay rights campaigner Peter Tatchell said the existence of both civil partnerships and marriage was a form of "sexual apartheid".

"To deny same sex marriages conducted in Canada the same recognition as heterosexual marriages in Canada strikes me as a case of overt discrimination," he said outside court.

The judge insisted heterosexual marriages and same-sex partnerships were not the same thing.

"Parliament has not called partnerships between persons of the same-sex marriage, not because they are considered inferior to the institution of marriage but because, as a matter of objective fact and common understanding ... they are indeed different," Potter said.

Human rights campaign group Liberty, which gave the couple legal support, said the ruling was wrong.

"I have no doubt that today's judgement will in due course be viewed as being out of step with contemporary values," Liberty legal officer Joanne Sawyer said in a statement.

But, Stonewall, a charity which campaigns for gay and lesbian equality, said civil partnership already gives couples the same legal and financial security as marriage.

"Civil partnership has all the rights of marriage anyway, including pensions," a Stonewall spokesman said. "There are a lot of gay couples out there that don't want it called marriage."

Family law solicitor Richard Hogwood, of lawyers Speechly Bircham, said the government would be relieved the ruling did not undermine the civil partnership law.

Had the couple won their case, the argument for same-sex marriage "would have been invested with a great deal more force," he said.