Tom Freeman and Katherine Doyle outside the registry office with their civil union application. (AAP)
A straight British couple who reject marriage but want to seal their love with a civil partnership have been told they could not because they are not gay.
Tom Freeman and Katherine Doyle, both 25-year-old civil servants, were turned away from Islington Registry Office in north London because the law says civil partnerships - recognised in England since 2005 - are only for same-sex couples.
Undeterred, the couple said they will take their fight for equality to court.
"We want to secure official status for our relationship in a way that supports the call for complete equality and is free of the negative connotations of marriage," Freeman said.
"If we cannot have a civil partnership, we will not get married."
A spokesman for Islington Council said: "The law dictates that a civil partnership is only for couples of the same sex. The council must follow the law."
There are a small number of differences between a marriage and a civil partnership, including that a marriage can be conducted in a church, while a civil partnership cannot.