Sir Menzies Campbell yesterday ruled out any notion of the Liberal Democrats forming a coalition with the SNP at Holyrood on the basis of agreeing to a referendum on independence for Scotland.

The LibDem leader also paved the way for a return, possibly this year, to his party's front bench of Charles Kennedy, who 12 months ago resigned the leadership after admitting to a drink problem.

Yesterday, Alex Salmond suggested that, were the Nationalists to become the largest party in the Scottish Parliament after May 3, then the Liberal Democrats would change their tune because the electorate would have given the SNP a "moral authority" to offer it a choice on independence.

The Nationalist leader has introduced an element of "flexibility" in the timing of when he would call an independence referendum should he gain the keys to Bute House in Edinburgh, because Mr Salmond knows he will need support from other parties to hold it.

He told GMTV the Liberal Democrats did not support an independence referendum "at present" but said that if the SNP were to gain the majority of Holyrood seats, then this would act as a "corrective".

"If the people effectively give an instruction by electing a party; say the SNP is our largest party; then you'll find most politicians will follow the people's lead; they'll accept that's a verdict of the electorate and try not to stand in the way of democracy."

He added: "We would have a lot of moral authority if we were the leading party and I don't think people would like to gainsay the verdict of the electorate."

However, Sir Menzies insisted Scottish LibDems were "not interested in a referendum on independence", declaring: "We will say flatly - no. That's what we have said in the past and that's what we are saying in the course of this quite well-extended election campaign."

He told the BBC: "We had a referendum whether or not we should have a parliament in Scotland in 1997. People expressed their views then. It's absolutely of fundamental importance to deal with issues such as health and education and the environment. People are concerned about their schools and their hospitals, not about yet more constitutional activity."

On Mr Kennedy, Sir Menzies said his colleague was pursuing other interests at present such as television work and writing.

Asked if he would like to see his predecessor back on the front bench, the LibDem leader replied: "Charles Kennedy has a rare talent in British politics: the ability to connect with the public, probably better than just about anyone else we can mention.

"It would be very foolish of us not to ensure that his talent is put to good use in the interests of the party."