THE prospect of a future SNP-LibDem coalition at Holyrood receded even further yesterday when Sir Menzies Campbell made clear that if Alex Salmond stuck to a policy of holding an independence referendum all bets would be off on a future alliance.

In an exclusive interview to mark the first anniversary of his leadership and as the party faithful gather in Harrogate for their spring conference, Sir Menzies dismissed the need for a referendum and suggested the politics of Nationalism and Liberalism did not mix.

Asked if he ruled out a coalition with the SNP if it stuck to its "non-negotiable" plan for an independence referendum, the Fife MP said: "That's what Jim Wallace said, it's what Nicol Stephen has said and I agree."

He went on: "If people want independence they can vote for the SNP in sufficient numbers. A referendum on top of a General Election would be an unnecessary distraction from the issues of health, education and the environment."

Asked if the Nationalists were xenophobic, as suggested by one LibDem MSP, Sir Menzies replied: "It's not the language I would have used. I'm not a Nationalist. I'm a Liberal. There is a sense in which Liberalism and Nationalism are the antithesis of each other."

He insisted that he defended Scotland's legal system, church and parliament "not because we are exclusive or better but because these are elements of the Scottish way of life which have great strength and in some respects virtues but I defend them from a Liberal point of view not an exclusive point of view".

Sir Menzies made clear it was a matter for Mr Stephen, party leader in Scotland, and his MSP colleagues how they approached the electoral arithmetic and decided what was "in the national interests of Scotland" on May 4.

He argued Scotland would forfeit much international influence if it went independent, for instance losing a seat on the UN Security Council. "Our ability to influence the kind of world we live in would be very severely dented," he stressed.

On Westminster and talk of him drawing up contingency in case his party held the balance of power after the next General Election, Sir Menzies said talk of hung parliaments was another distraction, adding: "But you would think it remiss of me not to be considering all the possible outcomes."

Sir Menzies said life as leader meant his weekends had "disappeared", there were 18-hour days, more responsibility and a greater volume and intensity of work. But he added: "There's a sense of excitement."

The early by-election triumph in the previously safe Labour seat of Dunfermline and West Fife and the near-miss in the previously safe Tory seat of Bromley and Chislehurst got Sir Menzies's stewardship off to a flying start.

Yet the honeymoon for David Cameron meant the LibDems always seemed one, if not two, steps behind.

The Tory leader's championing of green issues and his branding of his party as "liberal Conservatives" were regarded by LibDems as a blatant attempt to steal their political clothes.

Even their proposals for green taxes found resonance with the Conservatives' policy noises and their claim to be the new guardians of the environment.

Most annoyingly for Sir Menzies and his followers is how the Tory bounce in the polls has got higher at the expense of Labour and the Liberal Democrats.

Yet despite regularly polling below 20% - some even put his party on 14% - the commander-in-chief insisted the LibDems were "not in the doldrums". "At this stage in the parliament for us to be 20% is better than either Ashdown or Kennedy had when they were leader."

Twelve months into the "Ming dynasty", there are already claims - predicated again on the assertion that the leader at 65 is "too old" - that the Scot is under threat. "I have very good intelligence. There are no mumblings," he said. "If I did not think I was fit enough to do the job, I wouldn't be doing it."

Of course, Iraq is still the LibDems' most bankable policy with many voters. Sir Menzies's proposal of complete troop withdrawal by October has produced stinging rebukes but the party leader maintained it was "not a white flag to the insurgents" but a recognition that "we've done as much as we can".

May 4 will reveal whether the Iraq card is still the LibDems' ace.