A straight couple who were barred from having a civil partnership say they will fight the ban in court.
Ian Goggin and Kristin Skarsholt, of Bristol, said they were disappointed to have been rejected by Bristol register office because they are straight but hope that their attempt would help change the law.
The students, who are Quakers, are part of the Equal Love campaign.
The movement, organised by gay rights campaigner Peter Tatchell, will see eight couples – four gay and four straight – go to court to challenge the bans on gay marriage and straight civil partnerships.
Ms Skarsholt, 22, an Arabic student, said: “We are disappointed that we were not able to have our relationship legally recognised. Ian and I genuinely wish to secure legal recognition as civil partners. We are determined to fight through the courts to end the legal segregation that continues to keep straight and gay couples in separate institutions.
“Just as our gay friends are excluded from civil marriage, we are being excluded from having a civil partnership. This is discriminatory segregation on the basis of sexual orientation. It is wrong,” she added.
Mr Goggin, 21, who studies music technology, said: “Although the register staff were extremely helpful, they were unable to offer us a civil partnership. They felt obliged to act in accordance with the law as it currently stands. We thank them for their politeness. We regret this rejection but our resolve to carry on the campaign for equality remains strong.
“We are hopeful that our forthcoming legal case, led by Professor Robert Wintemute and Peter Tatchell, will eventually end discrimination against heterosexual couples in civil partnership law. Next time we come here to apply for a civil partnership we are confident there will be a happier outcome,” he said.
Commenting, Mr Tatchell said: “Our aim is to secure equality in civil marriage and civil partnership law. We want both systems open to all couples, gay and straight, so that everyone has a free and equal choice.”
He added: “Political support for ending the ban on gay marriage is growing. London mayor Boris Johnson, and former Conservative Party Vice-Chair, Margot James MP, have both come out in favour of allowing lesbian and gay couples to marry in a registry office, on the same terms as heterosexual partners.
“This view is also endorsed by the leader of the Labour Party, Ed Miliband, and by the deputy prime minister Nick Clegg of the Liberal Democrats.
“Both the Liberal Democrat and the Green party conferences have voted overwhelmingly in favour of ending the bans on gay civil marriages and heterosexual civil partnerships.”