Truro and Falmouth MP Sarah Newton, also a deputy chair of the Conservative Party, is defending herself from claims she broke a promise to her constituents after abstaining in this week’s vote of the Marriage (Same Sex Couples) Bill.

Mrs Newton said in a statement: “The clear majority of representations to me from constituents expressed opposition to the bill.

“As such, as promised to my constituents, I did not endorse the Marriage Bill at its third reading in recognition of the lack of endorsement of the bill’s contents from the people of Truro and Falmouth.

“A bill can only pass through the House of Commons if it is supported by votes in its favour.

“If the number of Members of Parliament who abstained or voted against the bill had outweighed the number of members who voted for it, the bill would not have been passed.

“My decision to withhold my personal mandate from the bill, thereby threatening its passage, was a direct reflection of the lack of a mandate that the bill received from Truro and Falmouth residents.”

The Cornish MP had previously said she personally supported proposals to allow same-sex couples to marry, but that her final voting decision rested on the outcome of a local equal marriage debate involving her constituents, which was held earlier this year in Truro.

The Marriage (Same Sex Couples) Bill passed its third reading in the House of Commons on Tuesday with a Commons majority of 205.

128 Conservative MPs voted against the bill.

Both of Mrs Newton’s Conservative colleagues in Cornwall also abstained from voting.

George Eustice, MP for Camborne and Redruth, is on his honeymoon and Sheryl Murray, MP for South East Cornwall, abstained.

All three Liberal Democrat Cornish MPs, Stephen Gilbert, Dan Rogerson and Andrew George, voted in favour.

Writing for PinkNews.co.uk earlier this week, Stephen Gilbert, MP for St Austell & Newquay, said: “I don’t doubt the prime minister’s personal commitment to delivering equal marriage. My concern is that David Cameron is in danger of being buffeted by the storms raging within his disunited party.”

Yesterday, David Cameron accepted that his party was divided on the issue but said: “I think it is right for Britain, like other countries, to take on this issue and to determine the right approach and that’s exactly what I’ve done and I’m proud of the fact that this legislation has now passed the House of Commons. That’s a good thing.”

Peers in the House of Lords will start debating the bill on 3 June.