After a day of confusion that threatened to disrupt the passage of the introduction of same-sex marriage, MPs have voted against the introduction of opposite sex civil partnerships.

70 MPs voted in favour of opposite sex civil partnerships, while 375 voted against the amendment. Earlier, 391 MPs to 57 voted in favour of an alternative amendment that promises for the Government to hold a speedy review of the future of civil partnerships that could include opening them up to opposite sex couples.

Tim Loughton, the anti-gay marriage Conservative MP who proposed the motion told MPs: “If the Government think it is right to extend marriage to everyone then it has to be right to extend civil partnerships to everyone too.”

He added: “This can only be good for improving stability for many more of the near three million opposite-sex couples who currently choose to cohabit but are in no formally recognised relationship.”

61% people who responded to the Government’s consultation said that they, unlike the Government, were in favour of opposite sex civil partnerships. Ministers and advisors have privately indicated to PinkNews.co.uk that there were strong arguments to ‘grandfather’ civil partnerships after same-sex marriage is introduced.

MPs from both sides of the debate on same-sex marriage spoke in favour of opposite sex civil partnerships. Most of the supporters of same-sex marriage argued that the issue should be considered separately to same-sex marriage.

Green MP Caroline Lucas said that she has supported equal civil partnership for years, but said she was surprised at the “politicking” with the amendment.

Ministers had earlier warned that straight civil partnerships could impose additional costs to the tax payer of as much as £4 billion because of pension and inheritance tax changes.