The former head of the Scottish Conservative Party has told constituents he will not be supporting the redefinition of marriage.
Edinburgh MSP David McLetchie argued that homosexual couples already had the same legal rights through civil partnerships and there was no reason for change.
Mr McLetchie said: “I welcome the establishment of civil partnerships in Scotland which means that civil partners now have the same legal rights and responsibilities as married couples in terms of their relationship with one another.
“Accordingly I do not see the need for further change.”
Organisations fighting to preserve the traditional definition of marriage believe homosexual groups should not have the right to redefine marriage for everyone and that people should not be intimidated into going along with it because of political correctness.
A spokesman for Scotland for Marriage, one such group, said: “Marriage is between one man and one woman.
“We draw on a well-researched evidence base which shows that, although death and divorce may prevent it, children do best when raised by their married mother and father.”
Same-sex marriage campaigners have been urging supporters across Scotland to contact their MSPs on the issue.
Later this month the Equality Network will hold a reception for the Equal Marriage campaign at the Scottish Parliament in Edinburgh.
It is being sponsored by MSPs from each of the main political parties, with Scottish Liberal Democrat leader Willie Rennie, Labour’s Jackie Baillie, SNP’s Joe Fitzpatrick and the Tories’ Jackson Carlaw all pledging their support.
The Scottish Government’s plans to redefine marriage have encountered widespread opposition, with church leaders from more than 70 of Scotland’s largest evangelical churches, representing more than 20,000 people, signing a petition against it.
Muslim leaders, the Church of Scotland, the Free Presbyterian Church of Scotland, the Scottish Episcopal Church and the Roman Catholic Church are all opposed to the move.
The deadline for consultation responses closed last month, as Christians eagerly await news of how the Scottish Government will deal with the matter.