The local MP of a straight couple who are fighting to get a civil partnership has said she is supporting them and will raise the issue in parliament.

Tom Freeman and Katherine Doyle, both 25 and of Holloway, London, were turned away from Islington’s registry office on Tuesday.

They are fighting for a civil partnership on the grounds that barring straight couples from accessing them is discriminatory. They argue that all institutions, including marriage, should be open to everyone regardless of sexual orientation.

Emily Thornberry, MP for Islington South and Finsbury, told the Islington Gazette she saw no reason why they could not have a civil partnership or gay couples could not get married.

She said: “They have not been to see me yet but I do support them fully. I can see no reason why they can’t have a civil partnership and gay people can’t get married in the same way. The first opportunity I have I will be raising this in parliament.”

Speaking outside Islington’s registry office on Tuesday morning, Freeman and Doyle said they were willing to take their case to the European Court of Human Rights if necessary.

Gay rights activist Peter Tatchell, who is supporting them, said that the ban may breach the European Convention of Human Rights with regard to articles eight, 12 and 14. These refer to a right to privacy, marriage and freedom from discrimination.