The ruling party will set out the timescale for such a move in its manifesto ahead of the Scottish Parliament election in 2016.

First Minister Nicola Sturgeon said the manifesto will include more details on the circumstances under which another vote might be "appropriate".

The revelation comes after Scots voted by 55% to 45% to reject leaving the union last September.

A recent survey for STV suggested 53% of voters in Scotland would back independence if there was another referendum.

The poll also put support for the SNP in next year's election at 55%, compared to Labour's 21%.

A Downing Street spokesperson said: "The people of Scotland voted to remain part of the United Kingdom last year.

"And we will see through our commitments to give them the extra powers in the Smith Agreement."

Since the independence result, the SNP has gained thousands of new members and won a landslide 56 of Scotland's 59 seats in May's general election.

Ahead of the party's conference in Aberdeen next month, Ms Sturgeon has been under pressure to clarify her position on a second vote.

She said: "Our manifesto will set out what we consider are the circumstances and the timescale on which a second referendum might be appropriate, but we can only propose.

"It's then for people in Scotland, whether it is in this election or in future elections, to decide whether they want to vote for our manifesto.

"And then if there is in the future another independence referendum, whether that's in five years or 10 years or whenever, it will be down to the people of Scotland to decide whether they want to vote for independence or not.

"So at every single stage this is something that is driven by and decided by the people of Scotland, not by politicians."