LIBERAL DEMOCRAT leader Menzies Campbell has suffered another challenge to his authority after one of his party's MSPs said he should be replaced by Charles Kennedy.

John Farquhar Munro, MSP for Ross, Skye and Inverness West, said Campbell had not been a success as leader as he was "not a good people person". He added that he would sign Kennedy's nomination papers today if asked to.

Campbell's future as leader was the subject of much speculation at last week's LibDem conference in Brighton.

His week got off to a poor start when party grandee Lord Rodgers attacked his performance as leader. "There is a feeling that there is a lack of energy and an absence of direction," he said.

This was followed by LibDem MP Nick Clegg stating that he would be likely to stand for the leadership if there was a vacancy.

Campbell's problems have been compounded by Munro, who believes Kennedy should make a return as leader. Kennedy resigned from the post last year after party colleagues confronted him over his alcohol problems.

Asked if he now believed Kennedy should replace Campbell, Munro said: "Yes I do, but after the next election," adding: "However, I would sign his nomination papers now, if he wanted it."

On the differences between the two Scottish LibDem MPs, he said: "Charles seemed to attract the electorate, but Ming is different. The main difference is not policy or promotion of policy, it's PR. Ming is not a good PR man, he is not a good people person."

Asked if he thought Campbell had been a success as leader, he said: "No, I don't think so. I don't think he has been the sort of enthusiastic, firebrand leader that we have needed at this time."

The remarks are likely to increase the tension between Campbell and Kennedy, the latter of whom has stopped short of ruling out a bid to return as leader.

Munro's comments will be seen as significant as he is one of Kennedy's closest allies. They represent the same area for different parliaments, and Munro is known to have co-operated with Greg Hurst's biography of Kennedy.

Munro's comments also reflect the lack of enthusiasm for Campbell's leadership within the MSP group. It was reported last year that a majority of LibDem MSPs had not supported his leadership bid.

Campbell said last night: "I have no comment to make."

His spokesman said: "There is no vacancy. Ming is there, he is up for it. To say he doesn't have the energy is untrue. As far as Charles is concerned, when he shows an interest, the front bench beckons. Relations between them are good."

A Scottish Liberal Democrats spokesman: "John is entitled to his opinion. He is well-known as a close friend of Charles, but it is interesting to note that he rejects the suggestion that there should be a change before the election."