David Cameron is in full support of equal marriage, and the matter of whether the Government supports equal marriage is not in question, a Downing Street spokesman has confirmed.

The source told PinkNews that, despite earlier reports that the Government would not rule out withdrawing its support for equal marriage, that passing it is David Cameron’s “paramount concern”, and that Downing Street would simply be deciding how best to make same-sex marriage legal, if an amendment to allow straight civil partnerships were to pass.

Three Tory MPs – Tim Loughton, Charlotte Leslie and Rob Wilson – are pushing for civil partnerships to be an option for heterosexual couples in an amendment as part of this week’s third reading of the Marriage (Same Sex Couples) Bill.

Culture Secretary and Minister for Equalities, Maria Miller has tabled a second amendment, which would mean a review for civil partnerships for straight couples, within five years of the introduction of equal marriage.

Labour MPs are being urged by Shadow Home Secretary and Minister for Women and Equalities, Yvette Cooper to vote in favour of a manuscript amendment, tabled by shadow equalities minister Kate Green MP, which would mean a consultation on straight civil partnerships, as soon as possible.

Some Tory MPs have told PinkNews that they will vote in favour of the Labour manuscript amendment, rather than the amendment tabled by Tim Loughton.

Ms Cooper said Labour’s manuscript amendment “would allow the [equal marriage] bill to keep making progress and to prevent either the government or some of the Tory backbenchers using this as an excuse to wreck the bill or to delay the bill. We don’t want anybody to use this as an excuse to wreck the bill, including the government.”

On the bill, Downing Street said the Government “has a legislative programme and it is getting on with it”, which has been taken as a signal that the Government will not drop the bill.

Liberal Democrat leader and Deputy Prime Minister Nick Clegg has said he will not allow Tory opponents to succeed in wrecking the Marriage (Same Sex Couples) Bill.