Transsexual or same-sex marriage is illegal under existing law, the House of Lords has ruled.

Passing judgement on Thursday, the Law Lords found that they had no power to change legislation regarding the recognition of transsexual partnerships.

Instead the senior judges said that such a change must wait until specific legislation had made its way through parliament.

The case was brought by Mrs Bellinger of Lincoln, after a succession of courts ruled that her 21-year marriage was void because of sex-change surgery undertaken in the early 1980s.

As UK law currently forbids same sex marriage the Lords were ruling on whether at the time of her marriage Mrs Bellinger could legally be recognised as a women.

Ruling on the original case brought by Mrs Bellinger, judge Gavin Lightman has said: "Sex is determined at birth and cannot subsequently be altered by any such operation as was undergone by the claimant."

Last July, the European Court decided that UK rules breached fundamental human rights and it was on this basis that Mrs Bellinger sought to challenge the annulment of her marriage.

The Lords accepted that "the criteria for designating a person as male or female are complex" but felt that such a substantive change to British law lay outside of the remit of the courts.

"This [case] raises a question which ought to be considered as part of an overall review of the most appropriate way to deal with the difficulties confronting transsexual people," said the ruling.

"A change in the law as sought by Mrs Bellinger must be a matter for deliberation and decision by parliament when the forthcoming Bill is introduced."

The Lord Chancellor's Department accepted the incompatibility of the ban on transsexual marriage with the Human Rights Act, and has promised to introduce measures to address the problem.

A transsexual support group, the Gender Trust, expressed its frustration with the ruling.

"This is a disappointing judgement for the Bellingers in particular and transsexual men and women in the UK in general," said a spokesman.

"Despite the European Court of Human Rights ruling last July that the inability of transsexual men and women in the UK to marry in their acquired gender was contrary to Article 12 of the European Convention on Human Rights, the Law Lords have confirmed earlier legal judgements in this case that it is for parliament to amend the law first.

"We urge the government to remedy this highly unsatisfactory situation by pushing ahead with their proposed legislative changes announced last December without further delay."