Mr Freeman and Miss Doyle plan to take legal action
A heterosexual couple have been refused permission to register for a civil partnership.
Tom Freeman and Katherine Doyle said they want to challenge "discriminatory" UK laws which restrict civil partnerships to same-sex couples.
They plan legal action after their application was denied at Islington Register Office, north London.
A spokesman for Islington Council said the pair's request was refused because "the council must follow the law".
UK law permits only heterosexual couples to marry; same-sex couples can form civil partnerships.
Couples in a civil partnership have the right to the same legal treatment across a range of matters as a married couple - including inheritance, pension, life assurance and maintenance rights.
However civil partnerships can only be conducted by registrars, not members of the clergy, and the partnership cannot legally be called a "marriage".
Mr Freeman and Miss Doyle, both 25, from Islington, have been in a relationship for four years.
Mr Freeman said: "It would be lovely to formalise our relationship but we are completely turned off by the whole institution of marriage because it discriminates against gay people."
He added: "We think gay people should be able to have a standard marriage and straight people should be able to have a civil partnership."
Miss Doyle said: "We want a choice and all other couples should also have a choice, irrespective of their sexuality."
Their bid was supported by human rights campaigner Peter Tatchell.
Mr Tatchell said: "The ban on heterosexual civil partnerships is heterophobic. It is disciminatory and offensive."
He added: "I applaud their challenge to this unjust legislation."
An Islington Council spokesman said: "The law dictates that a civil partnership is only for couples of the same sex.
"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."