Former Government minister Tim Loughton was sacked because of his opposition to redefining marriage, according to reports.
He was removed from his ministerial post in September’s Government reshuffle, and close friends say it was because of his support for keeping marriage as it is.
Mr Loughton voted against the Marriage (Same Sex Couples) Bill on Tuesday night, together with over 170 other MPs.
One Tory MP told the Scotsman newspaper: “Tim was a really good minister whose career was wrecked because of his stance on this issue on a matter of principle.
“It shows that, already, this bill is poisoning the party and destroying careers.”
David Cameron promised that Tory MPs would have a free vote, but behind the scenes a lot of pressure was applied to stop them breaking rank.
Another MP said: “The fact that the result was still 136 against to 127 in favour [among Tory MPs] after those tactics just goes to show that the Prime Minister has lost his authority.”
There are now rumours that David Cameron may face a leadership challenge in the wake of the gay marriage vote if the party comes third in the forthcoming Eastleigh by-election.
The Eastleigh seat has been made vacant by the resignation of Liberal Democrat MP Chris Huhne.