A spokesman for Eamon Gilmore has said that legislation allowing adoption by same-sex couples would have to be in place before any referendum on same-sex marriage was held.

An equal right to adoption for same-sex couples would mean that children no longer had a preferential right to be raised by a mother and a father where possible.

The statement came as it emerged that many Fine Gael TDs expressed unease at a promise made by Tanaiste Eamon Gilmore at the weekend to hold a referendum to redefine marriage.

Mr Gilmore told a Labour Youth conference at the weekend that he believed that there would be a referendum in the lifetime of the Government.

He said that the autumn of next year or the spring of 2015 were possible dates.

However a spokesman for Mr Gilmore said that the issue of gay adoption had to be dealt with in legislation beforehand to prevent it from overshadowing the gay marriage referendum.

“Any referendum that takes place will have to be about marriage equality and not about other issues,” he told The Irish Independent.  

Presently, gay or lesbian people can adopt a child on their own, but not as a couple.  

Justice Minister Alan Shatter is already preparing legislation to allow same-sex couples rights in relation to guardianship and the custody of children.

Children’s Minister Frances Fitzgerald is also working on new adoption legislation. But cabinet agreement would be required to include same-sex adoption in either piece of legislation.

The cabinet is set to consider the issue of a referendum on same-sex marriage in the next two weeks after the Constitutional Convention think-tank recommended that it be held.

Although Mr Gilmore has described gay marriage as the “civil rights issue of this generation”, Taoiseach Enda Kenny has not declared his position on gay marriage or gay adoption.

A spokesman for Mr Kenny said he would not be commenting on the issue ahead of the cabinet discussions.

There is an acceptance among Labour and Fine Gael ministers that any vote will need to be carefully planned given the ‘referendum fatigue’ obvious in the 39pc turnout for the Seanad and Court of Appeal referendums earlier this month.

Reports suggest that many Fine Gael TDs are wary of a referendum on same-sex marriage.

While the immediate setting of a date for a referendum is unlikely, Fine Gael TDs acknowledged divergent views within the parliamentary party on the merits of proceeding with a vote at all, the Irish Times reports.

Sources say that while some are mainly worried about the political fallout in the wake of the Seanad referendum defeat, others are opposed to the substance of the proposal itself.

There is also a worry that such a referendum might lead to further divisions within the party, after the deeply divisive vote on abortion legislation.

Dublin South-East Fine Gael TD Eoghan Murphy told the Irish Times that he supported the holding of a referendum on same-sex marriage, but that he didn’t think the party were obliged to take a position during the referendum.  

However another TD, who declined to be named said that the Government’s job was “to get the economy back on track, to get all that right, that’s ultimately what we’ll be judged on”.  

He said: “My own opinion is that we should concentrate over the next two years on economy and jobs.”

When it was put to him that Mr Gilmore had cast same-sex marriage as the civil rights issue of our time, the TD said: “I think it’ll be in Labour’s interest as well to follow what I just said.”