A heterosexual couple have lost their Court of Appeal battle to have a civil partnership instead of a marriage.
Rebecca Steinfeld and Charles Keidan, from London, challenged a ruling that said they did not meet the legal requirement of being the same sex.
The judges said there was a potential breach of their human rights, but the government should have more time to decide the future of civil partnership.
The couple said there was still “everything to fight for”.
They intend to appeal to the Supreme Court.
A government spokesman said it welcomed the ruling and would take the judgement into account during its evaluation of civil partnerships.
The BBC’s legal affairs correspondent Clive Coleman said the couple had lost by the “narrowest of margins”.
Our correspondent said: “The government’s ‘wait and see’ policy, which is based on looking at the take-up of same-sex civil partnerships, was found by Lady Justice Arden not to be not good enough to address the discrimination faced by heterosexual couples.
“However, her fellow judges were prepared to let the government have a little more time and so the case was lost on that issue alone.”
Kate Stewart and Matthew Cole, 46, decided to get a civil partnership in Gibraltar, a British Overseas Territory, in June 2016, after deciding marriage was not for them.
“Matthew and I didn’t feel that marriage reflected our relationship,” said Dr Stewart, from Derby.
“The institution [of marriage] is very much unequal depending on your religion.
“We therefore felt it wasn’t a status we were comfortable with because it still had hangovers of inequality from the past.”
Dr Stewart, 48, said although they believed marriage was right for some couples, it was about having the choice.
They wanted recognition of their relationship after 10 years together, although their civil partnership is still not legally recognised in the UK.
“We paid for the ceremony in pounds, we have a certificate, it was all very British, but as soon as we were back home we didn’t have legal recognition,” Dr Stewart said.
“The declaration that we were both each other’s partner was quite moving… we were on an equal footing. It was surprisingly touching.”
Ms Steinfeld, 35, and Mr Keidan, 40, want to secure legal recognition of their seven-year relationship but do not consider marriage suitable for them.
The couple, who have a 20-month-old daughter, have said they want to formalise their relationship within a social institution “which is modern, which is symmetrical and that focuses on equality, which is exactly what a civil partnership is”.
“We lost on a technicality,” Ms Steinfeld said.
“So there’s everything to fight for, and much in the ruling that gives us reason to be positive and keep going.”
Dan Squires, QC for the secretary of state for education, who has responsibility for equalities within government, said it had been decided at this stage not to extend civil partnerships to opposite-sex couples, or to either abolish or phase them out.
Instead, he said the government planned to see how extending marriage to same-sex couples impacted on civil partnerships before making a final decision.
All three judges agreed that the status quo could not continue indefinitely.
Human rights campaigner Peter Tatchell, who supported Ms Steinfeld and Mr Keidan in court, said the ruling was “a defeat for love and equality”.
“It cannot be right that lesbian and gay couples have two options, civil partnership and civil marriage; whereas opposite-sex partners have only one option, marriage,” he said.
Education campaigner and journalist Fiona Millar, who has been in a relationship with journalist Alastair Campbell for 35 years, told the court they had chosen not to get married “on principle”.
After the ruling, she said she was “one of thousands and thousands” of people in the UK who will be waiting for the government to “close the civil partnerships loophole by making them available to all”.