Peter Tatchell has suggested that the government is likely to decline opening up civil partnerships to heterosexual couples, when it issues its official response to the equal marriage consultation, later this month.

In a statement, the human rights campaigner said: “Despite proclaiming that the legalisation of same-sex civil marriage is driven by the principle of equality, David Cameron is expected to retain the inequality of the current legal ban on heterosexual civil partnerships.

“Opposite-sex couples are legally prohibited from having a civil partnership and David Cameron intends to keep it that way.

“This will mean gay couples will soon have legal privileges over heterosexual couples”.

Mr Tatchell went on to say: “There will be two forms of official state recognition for lesbian and gay couples: the present system of civil partnerships and the new system of civil marriages. Heterosexual couples will have only one option: marriage.

“They will be subjected to legal inequality and discrimination.

“This is very wrong. I support straight equality.”

Speaking at the Liberal Democrat Conference in September, International Development Minister Lynne Featherstone, who was previously the junior equalities minister until this year’s reshuffle, stated that reforming civil partnership legislation should be done separately to same-sex marriage reform.

The Lib Dem MP told an LGBT fringe event that discussions about heterosexual civil partnerships should be incorporated into a wider debate concerning co-habitation rights.