Two British women who were married in Canada have gone to the High Court in a test case to win legal recognition for same-sex couples who marry abroad.
The University professors Sue Wilkinson and Celia Kitzinger, who live in north Yorkshire, argue that UK laws which validated their union as a "civil partnership" do not go far enough.
Lawyers for the couple argued at the High Court that if a heterosexual couple were married in Canada and then returned to England their marriage would be automatically recognised and registered.
The University of York and Loughborough University academics were declared "wife and wife" in a 2003 ceremony in Canada.
The Civil Partnership Act, introduced in December last year, gave gay partners in the UK many of the rights enjoyed by married heterosexuals.
But the act states that same-sex couples who marry in countries where such marriages are lawful "are to be treated as having formed a civil partnership".
The couple, who have been together for 16 years, said it was "insulting and discriminatory" to be offered civil partnership instead of marriage.
In a statement read to the High Court, Ms Wilkinson said: "It is important to both of us that we are recognised as partners in life by the world at large."
Karon Monaghan, the barrister representing the couple, said laws prohibiting marriage between different social classes or religions had long been repealed but there were still laws banning same sex partners from marrying.
If the factors preventing the marriage being recognised were because the couple were black or of mixed race, "it will be very clear that such laws are repugnant", she said.
"There is no real difference between such laws of exclusion. Having regard to the Human Rights Act, such laws cannot survive."
Professor Kitzinger, 49, is a sociology professor at the University of York. Professor Wilkinson, 52, a professor of psychology, is based at Loughborough University, Leicestershire, but was living and working in Vancouver at the time of the marriage.
The test case - one of several around the world - is being backed by human-rights group Liberty, which is providing legal representation, and supported by the gay rights campaign OutRage!, which sees the case as a bid to end "sexual apartheid and institutional homophobia".
In a statement issued through Liberty, the couple said they were married in a conservatory in Yaletown. "We made our vows: 'With this ring, as a symbol of my love and commitment, I call on those present to witness that I Celia/Sue do take you Sue/Celia to be my lawful wedded wife, to have and to hold, from this day forward, through all our life together'."
The marriage commissioner declared: "Upon the authority vested in me by the Province of British Columbia, I now declare you wife and wife'."
The couple said: "The decision to marry was an affirmation of our love and our commitment to each other. Being granted full social equality through marriage was of profound symbolic importance to us, especially for Celia, who first came out as lesbian as a teenager more than 30 years ago, when homosexuality was still treated as a psychiatric illness. I never expected to have the opportunity to marry someone I loved."
The couple added: "Our case is fundamentally about equality. We want to be treated the same way as any heterosexual couple who marries abroad - to have our valid Canadian marriage recognised as a marriage in our home country."
The couple's legal challenge came on the same day that the Catholic Church issued a denunciation of marriages between same-sex couples. The Vatican said that gay marriage and lesbians wanting to bear children were a threat to the traditional family and signs of "the eclipse of God".
A document, called "Family and Human Procreation," was published just days after US President George Bush urged the Senate to pass a constitutional ban on same-sex marriage.
The document said the family was under attack around the world, even in traditionally Christian cultures, by what it called "radical currents" proposing new family models.