Alex Salmond has raised the possibility of a second referendum on Scottish independence as he accused the three main UK parties of preparing to "betray" Scotland on more powers for Holyrood.

The First Minister suggested a "huge gap" was emerging between the vow given by David Cameron, Ed Miliband and Nick Clegg ahead of the referendum vote and the current plans for more Scottish devolution, which were being talked about.

"Right now, the initial judgement that's coming from Scotland is that people have no confidence in Tory guarantees and are absolutely fizzing about what looks like a preparation for a betrayal of a strong commitment made," declared Mr Salmond.

He claimed the Prime Minister had "started the process for reneging on the commitment" within an hour of the referendum vote when he appeared in Downing Street to talk about English votes for English laws.

Stressing that Scottish independence was the answer to the West Lothian Question, Mr Salmond noted how he had earlier said that the referendum was a "once-in-a-lifetime opportunity" and that constitutional referendums came along every 20 years or so.

But he then declared: "Circumstances obviously can change," and noted how if the UK party leaders' reneged in any way on their vow, then that would be a "very, very substantial change in circumstances".

The FM stressed that, ultimately, it was up to the people of Scotland to decide whether or not they had been "conned and tricked by Westminster".

But William Hague, the Commons Leader, insisted the vow to give the Scottish Parliament increased powers had not been broken.

"Alex Salmond is almost looking for and hoping for some sense of betrayal," he declared, "but let it me be very clear that every commitment made by not only the Conservatives but the Labour and Liberal Democrat parties about what would happen if the result of the Scottish referendum was No, every commitment has so far been kept and will be."

Stressing that all the leaders of the main UK parties had been absolutely unequivocal that the commitment to Scotland would be met, he added: "So there is no reneging here, however much it might suit Scottish Nationalists to try to say that there is."