Lord Ashcroft has looked into the Conservative Party’s voter polls in order to calibrate the varied reaction to Prime Minister David Cameron’s pledge to legalise marriage equality.

Earlier this week, the Coalition for Marriage published a poll which indicated that the plans for marriage equality could cost the Conservatives support among churchgoers.

Shortly after, the Mayor of London Boris Johnson released a video via Out4Marriage in which he reiterated his support for a change in the law.

Writing for Conservative Home, Lord Ashcroft said: “The intervention of the Mayor shows that the debate is not just one of left versus right within the Conservative Party, if indeed that delineation still applies.

“More importantly, it is a reminder that dropping the proposals in order to mollify one group of voters – as opponents of gay marriage advise – would have repercussions of its own.”

His study found that, overall, 42% were for marriage equality – with 31% against it. A quarter of those in favour (1% of all voters) said they would be more likely to vote for a party that changed the law to allow marriage equality and three-quarters (a third of all voters) said they were in favour of the idea – but the issue would not make any difference to how they voted.

Of those against marriage equality, the majority said the issue would not make any difference to how they voted, but just over a third (12% of all voters) said they would be less likely to vote for a party that introduced it.

Just over a quarter (27%) said they had “no opinion on this issue.”

Lord Ashcroft added: “Most people had not heard the issue was on the agenda. When it was raised, they tended to be very relaxed about the idea.

“By far the most common reaction was that if gay people wanted to get married, by all means let them get on with it; if the church did not want to take part, it should not (and need not) be compelled to.

“Many also felt that such a change was part of the development of a more equal and accepting society. Some admitted to being uncomfortable with the idea (“I still can’t get my head around it”), but they did not suggest that marriage in general, or their own marriage in particular, would be undermined or devalued by the proposed change.”

Earlier this week, the Evening Standard ran an editorial stating that Prime Minister David Cameron should not bow to those in his party who are resisting the idea of marriage equality.

The editorial said: “Whatever the reaction of some in his own party — and some Cabinet ministers are at best lukewarm — gay marriage would mark a fundamental extension of basic rights to gay people.”

It also said the PM should be proud for people to see he wasn’t afraid of continuing to modernise the Tories, and that it was “the right thing to do”.

Lord Ashcroft concluded that the issue for many transcended politics, and that it was: “one of principle on which public opinion is effectively immaterial.”

He added: “Of course MPs who feel this should vote with their consciences. But those who argue that gay marriage is a clear-cut net vote loser – and that abandoning the idea would help the Conservatives towards a majority – should examine the evidence more carefully.”