I knew I had been toiling a bit over recent months

Donald Dewar

The 62-year-old said he had "pretty good staying power" and looked forward to returning to work in "improved form" after surgery at Glasgow Royal Infirmary within the next few weeks.

After reacting to reports that the condition would force him out of office, Mr Dewar then rejected speculation that his absence would lead to rifts between the Labour and Liberal Democrats coalition partners.

Mr Dewar said both parties would work in the common interest but while Lib Dem leader and Deputy First Minister Jim Wallace automatically takes over his ministerial responsibilities, he would not be in charge of the executive.

The MSP for Glasgow Anniesland, who has been renowned for his energetic approach to politics, revealed that he was forced to accept something was wrong with his health when he began to slow down.

Donald Dewar: " I have been toiling"

He said: "I knew I had been toiling a bit over recent months. If I want to be complacent I would say that I've got pretty good staying power.

"I was aware I wasn't performing as well as I should but I think one of the things I was awfully glad about was there was a definable problem with a solution."

Mr Dewar said he asked doctors what the prospects were for him after surgery and was given a positive reply.

"It may not encourage everyone to hear this but they say there is no reason why I should not be back and in improved form.

"It's going to be a bruising couple of months but I'm looking forward to getting back into harness."

A tough week for JIm Wallace

However, Mr Dewar said that if the party and Scottish Cabinet indicated that he should stand down, he would give in to their will.

"The last thing you want is people clinging to office and the last thing you want is people being evicted, shunted out by indignant colleagues.

"So long as it's working and working there for the common interest, I'll be there, ready to serve."

Meanwhile, Labour and Lib Dem ministers have been preparing to draw up plans for liaison during Mr Dewar's projected three month absence.

They will seek to head off any further confusion following last week's debate on warrant sales in which Mr Wallace, in Mr Dewar's absence, continued to oppose Socialist MSP Tommy Sheridan's bill proposing their removal, unaware that Labour backbenchers had forced a climbdown by the executive.

The controversy left members of Mr Wallace's party angry and prompted allegations of chaos within the executive.