The prospect of a multi-option referendum on Scotland's constitutional future in two years' time received a significant boost yesterday when Tavish Scott, the new leader of the Scots Liberal Democrats, suggested that his party could back such a poll.

Mr Scott, speaking only minutes after winning a crushing victory over two rival candidates in the contest to succeed Nicol Stephen, indicated that he had watered down his opposition to a referendum but wanted Scots to have the option of voting for more powers for Holyrood as well as independence or the status quo.

Until now, the Lib Dems have steadfastly opposed any Nationalist referendum that could threaten the future of the Union and this “red line” led the party last year to reject coalition talks with the SNP after it won power in the Holyrood election.

However, asked yesterday whether that was still the position, Mr Scott said: “We will see what legislation the SNP comes forward with. I am not intuitively against making sure that people have a choice and opportunity to vote on these things, but I believe it should be for a strengthened Scotland within the UK.”

Alex Salmond, the Nationalist First Minister, is committed to holding a referendum on separation in 2010 although, until now, most observers have doubted that he would get enough votes in the Scottish Parliament for such a plebiscite.

If it did go ahead, according to the SNP, Scots would be asked whether they backed Nationalist ministers starting negotiations with Westminster on the terms for Scotland breaking away from the rest of the UK.

However, Mr Salmond has not ruled out the option of holding a multi-option referendum that could include the recommendations of the Calman Commission, set up by all three Unionist parties at Holyrood - Labour, Conservatives and Lib Dems - on extending Holyrood's powers within the UK. The commission is due to report by the end of this year.

If the Lib Dems were to support such a referendum, it would change the parliamentary arithmetic dramatically. Mr Salmond is already assured of support from two Green MSPs and an Independent MSP and the backing of the Lib Dems would be enough to give the SNP enough votes to hold it.

A spokesman for Mr Salmond said that Mr Scott had been known for his previous opposition to any referendum. “Today's statement shows some progress in that position, which we welcome. We look forward to him showing some early leadership and making absolutely clear that he will support a referendum Bill in 2010.”

Labour, the main opposition party at Holyrood, performed a series of U-turns this year on an independence referendum after Wendy Alexnder, the former leader, challenged Mr Salmond to “bring it on”.

Labour's position now appears to be that it will wait to see what legislation Mr Salmond comes forward with and that it would want to see the nature of the question to be asked.

However, Labour MSPs are believed to feel that they could never bring themselves to support a referendum, even a multi-option one, if it included the independence option. Gordon Brown is also opposed to such a referendum.

The Conservatives' position appears to be that the party would not back a simple “yes-no” independence poll, but would await the conclusions of the commission before making a decision on a multi-option poll.

The referendum issue raised by Mr Scott succeeded in overshadowing his leadership election victory, in which he polled 1,450 votes ( 59 per cent). Ross Finnie, the former environment minister, came second with 568 votes (23.1 per cent) and Mike Rumbles, the backbench MSP, came third with 439 votes (17.9 per cent).

Most observers were surprised by the scale of Mr Scott's victory, which was achieved on first preference votes.

In his victory speech Mr Scott claimed that he had won “the gold medal of the Liberal Democrats Olympics”, before attacking Mr Salmond as “politically dishonest”.

“We can already see the underlying weakness that will undo Alex Salmond. What looks confident, sure-footed and wise today will be seen as arrogant, misguided and politically dishonest tomorrow,” he added.

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