Tory MP Tim Loughton has said he believes around 139 Conservative MPs voted against the same sex marriage bill, and possibly as many as 40 of them abstained.
If true, that would mean that a substantial majority of the party did not vote with the Prime Minister.
He told BBC News that he did not see it as a reflection on David Cameron's lack of authority.
The Education Secretary Michael Gove has denied any knowledge of who in his department described an outgoing minister as a"lazy, incompetent narcissist obsessed only with self-promotion".
Tim Loughton, who was sacked as children's minister in the last reshuffle, was denounced in a briefing to the Spectator magazine by an anonymous source in Department for Education.
Mr Gove insisted he did not know who made the briefing and said Mr Loughton "far from being incompetent ... was a talented and effective minister who made a difference".