SCOTTISH Tory leader Ruth Davidson has joined other leading members of her party, including Boris Johnson and Michael Gove, in backing reform at Westminster legalising gay marriage.

As in Holyrood plans, it is proposed that in England and Wales churches that wish to opt out of such ceremonies would have that right.

The London Mayor and the Education Secretary are the highest-profile Tory backers of the plan at Westminster, where more than 100 of the party's MPs are likely to oppose the move. Explaining why Ms Davidson was supporting the reform, a spokesman said: "Ruth has always made her position clear on same-sex marriage.

"She supports the principle, with the proviso that religious organisations which do not wish to carry out the ceremony are not compelled to do so. Ruth has confirmed that, similar to other parties, Conservative MSPs will be given a free vote on the issue when the SNP Government brings it to the chamber."

Mr Johnson said the Government should "whack through" the gay marriage legislation, saying: "It is perfectly obvious that the constituency is there for doing this. No religion is going to be under any compulsion to change their observances. Whack it through. Let's knock this thing on the head."

The Mayor conceded his own position had shifted after opposing gay marriage some years ago. But he said the world had also changed, and appealed for Tory opponents to focus on other issues. He added: "I think it is a shame the subject continues to be so prevalent. Let's get it done and talk about the real Conservative things we want to do."