Two British women who were married in Canada have this morning begun a High Court battle to have their marriage recognised under UK law.

Sue Wilkinson and Celia Kitzinger, both university professors who married in August 2003, say that Britain’s new laws that validate their union as a civil partnership are not good enough.

The couple, who live in Yorkshire, want their Canadian marriage to be granted full legal status in Britain and insist that the offer of a civil partnership is an "insulting and discriminatory" alternative.

They argue that if a heterosexual couple were married in Canada and subsequently returned to England, their marriage would be automatically recognised in the United Kingdom.

The UK’s Civil Partnership Act, introduced in December, gives gay and lesbian partners many of the rights enjoyed by married heterosexuals. But it states that same-sex couples who marry overseas in countries where gay and lesbian marriages are lawful "are to be treated as having formed a civil partnership".

They want their marriage to be validated under the 1986 Family Law Act and are seeking a plea for a "declaration of validity of marriage" before Sir Mark Potter, President of The Family Division.

Their lawyers argue that failure to give such validity is a breach of the European Convention on Human Rights and the 1988 Human Rights Act, in particular the right to respect for private and family life, the right to marry and the prohibition against discrimination.

If the High Court finds in their favour it will need to rule that the Civil Partnership Act is incompatible with Britain's human rights laws. Lawyers said the CPA would then need to be amended in parliament.

The two women said the Civil Partnership Act was an important step forward for lesbian and gay rights which made "a huge practical difference to our ability to protect our loved ones". But they argue that to preserve the institution of marriage for different-sex couples sent out the message that lesbian and gay relationships were not worthy of recognition through marriage. "This discrimination is demeaning and unjust," they said.

Julian Washington, a private client partner at Forsters, said the women face an "uphill struggle" to get their marriage recognised.

"The Civil Partnership Act addresses all of the practical needs such as tax and estate planning that same-sex couples campaigned on for years. From a purely pragmatic point of view, it does the job," he said.

The two women , who have been together for 16 years, wed in British Columbia, one of the first jurisdictions in the world to recognise same-sex marriages.

Ms Kitzinger, 49, is a sociology professor at the University of York. Ms Wilkinson, 52, a professor of psychology, is based at Loughborough University, but was living and working in Vancouver at the time of their marriage.

Their legal move is backed by human rights group Liberty, which is providing legal representation. The case will be heard over four days.

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