Sue Wilkinson, 49, and Celia Kitzinger, 52, wed in Vancouver, Canada, in 2003 and had asked London's High Court for legal recognition of the marriage. They argued that their relationship was like that of any other married couple and that, by calling it a civil partnership, Britain had violated their human rights.
Mark Potter, president of the High Court's Family Division, ruled there was a "long-standing definition and acceptance" that marriage refers to a relationship between a man and a woman, primarily intended to raise children.
"To accord a same-sex relationship the title and status of marriage would be to fly in the face of the (European) Convention (on Human Rights) as well as to fail to recognize physical reality," Potter said.
However, Potter said lasting single-sex relationships were "in no way inferior" to relationships between a man and women.
"We are deeply disappointed by the judgment, not just for ourselves but for other gay couples and families," Wilkinson said after walking from the courtroom holding Kitzinger's hand. "It perpetuates discrimination and it sends out the message that lesbian and gay marriages are inferior."
Potter said that he believed people across England and Europe respected the concept of marriage and believed it was an important means of protecting the traditional family unit.
"The belief that this form of relationship is the one which best encourages stability in a well-regulated society is not a disreputable or outmoded notion based upon ideas of exclusivity, marginalization, disapproval or discrimination against homosexuals," Potter said.
Wilkinson and Kitzinger were told by Potter they have the right to challenge the ruling at Britain's Court of Appeal.
But Kitzinger said their life's savings have been exhausted by the court's decision that they must pay the government's $46,590 in legal costs.
"We are hopeful we will be able to appeal but need help to fund the cost, which will likely be the same amount again," Kitzinger told The Associated Press.
"Though we're disappointed, we are sure there will be a day — within our lifetimes — when there will be equality for same-sex marriage," she said. "This judgment will not stand the test of time."
The Netherlands, Canada, Belgium and Spain have legalized same-sex marriage, while several other European countries have laws similar to Britain's where same-sex couples have the right to form legally binding civil partnerships, entitling them to most of the same tax and pension rights as married couples.
In the United States, only the state of Massachusetts allows gay marriage, while Vermont and Connecticut permit civil unions.