A couple who want to become the first heterosexuals in Britain to have a civil partnership said they would begin a legal challenge after a council refused their request today .

Tom Freeman and Katherine Doyle, both 25, want the same legal rights as any husband and wife, but said they did not want to be seen to be "colluding with the segregation that exists in matrimonial law between gay civil partnerships and straight civil marriage".

The couple applied for a civil partnership at Islington register office, in north London, but were refused because UK law bans opposite-sex civil partnerships.

Freeman and Doyle, who are supported by the human rights campaigner Peter Tatchell, plan to seek legal advice.

"If necessary, we are ready to take our appeal all the way to the European court of human rights," said Freeman, a civil servant.

In a joint statement, the pair said they were "saddened and disappointed" that they had been refused because of their sexuality.

"In a democratic state, all institutions should be open to all people," the statement added.

Tatchell said the couple had a "tough legal battle" ahead of them, adding that they would "need lots of support".

"This is the first ever challenge to the ban on heterosexual couples having a civil partnership," he said.

"Tom and Katherine will first have to challenge this refusal through the British courts and, if this fails, then appeal to the European court of human rights in Strasbourg.

"Although I have spent much of my life campaigning against homophobia, I am equally opposed to heterophobic discrimination. I applaud Katherine and Tom and support their bid for heterosexual equality."

An Islington council spokesman said the law "dictates that a civil partnership is only for couples of the same sex".

He added: "The council must follow the law, of course, and so we have not been able to accept Mr Freeman and Ms Doyle's application for a civil partnership."