A minister in the Free Church of Scotland is urging MSPs to seriously consider the long-term consequences of legalising gay marriage.

The Reverend David Robertson, who is also director of the Solas Centre for Public Christianity, said changing the law would result in greater intolerance towards those who believe in a traditional definition of marriage as a union between one man and one woman.

"The gay rights groups, funded by the Scottish Government, will continue to push for Scotland not just to be 'tolerant' of gay marriage, but intolerant of any who do not accept their agenda," he said.

"There will be more pressure for social 're-education' through popular media, the education system and the social welfare and political systems.

"The attack on the traditional understanding of marriage will not be the end of this assault on Christian morality and values.

"We urge our MSPs to take this into account and at the very least make an informed decision thinking about the long term consequences, rather than merely the short term sound bites and media pressure."

Mr Robertson made the comments in a written submission to the Equal Opportunities Committee, which is scrutinising the Marriage and Civil Partnership Bill.

He was due to appear before MSPs at the Scottish Parliament on Thursday representing the Free Church's position.

In his submission, Mr Robertson said changing the definition of marriage to include same-sex unions would undermine the Christian foundations of Scottish society and lead to "further social disintegration, sexual confusion and greater intolerance".

He warned of a situation where people in public life or service who dare to uphold the Christian view of marriage "will be ostracised and discriminated against".

"If the Scottish Parliament takes the step of redefining marriage rather than displaying boldness, fairness and wisdom, we believe it will demonstrate cowardice, injustice and folly," he said.

"We therefore request that the Parliament do not take such a retrograde and reactionary step and we would ask you to refuse the request to redefine marriage."