But the equal opportunities committee also heard concerns that the Marriage and Civil Partnership (Scotland) Bill could lead to individual ministers being unable to refuse on grounds of religious conscience to conduct gay marriage ceremonies.
A report from the committee highlights concerns that safeguards in the bill for such ministers may not be enough to prevent a legal challenge.
The Church of Scotland has already said it may stop conducting weddings altogether amid concerns over the legal threat, the committee was told.
The report warns of “deep concern” within the Church of Scotland that the legislation will “unravel” with plenty of legal opinion to back this up.
“I think that in a short space of time, schools that do not teach the new morality and charities that do not accept the new morality will be legislated against,” Rev Alan MacDonald of the Church of Scotland told MSPs in evidence.
“In fact I do not think that there will need to be legislation – I think the courts will find against and we will get hammered.”
Churches must opt in before conducting gay marriages, under the terms of the bill.
But the committee also heard that this is unlikely to allow individual ministers to refuse to conduct a gay marriage on the grounds of religious conscience.
Aidan O’Neill QC, of Matrix Chambers, warned that ministers would not be in a position to refuse to conduct gay marriage ceremonies if their church had opted in.
“That doesn’t seem to be possible,” he told MSPs.
Karon Monaghan QC, also from Matrix Chambers, indicated that this safeguard could be open to challenge.
The first same-sex marriages are likely to be held in Scotland in 2015 if the new law is passed. It already has the support of the Scottish Government and a majority of MSPs have indicated they will back it.
But the proposal has provoked a backlash from faith groups who fear that it could undermine the status of marriage.
A public consultation produced 77,000 responses with two-thirds opposing the change, although social attitudes surveys have indicated that most Scots support it.
The issue will come before all MSPs at Holyrood for a vote on the general principles before the end of the month.
Tom French, policy coordinator for the Equality Network, said: “With just days to go before the crucial stage-one vote on the equal marriage bill, we urge MSPs to stand up for a fairer and more equal Scotland by giving this milestone legislation their full support.
“This bill will remove discrimination from the law and send out an important message about the kind of country we are.”