Mr Raffan is one of the Lib Dems' more colourful characters

Liberal Democrat Keith Raffan, 55, list MSP for Mid Scotland and Fife, has written to Presiding Officer George Reid tendering his resignation.

Mr Raffan has had lengthy absences from the parliament due to ill-health. Last month he topped the list for MSPs' expenses, claiming �108,826.

He is expected to be succeeded by Fife councillor Andrew Arbuckle.

Mr Raffan, who is believed to suffer from a back problem, said: "Due to the state of my health, it was probable that I would stand down during this parliament.

Over the last two years, it has been an uphill struggle to keep on top of my job Keith Raffan

"For over a year now, my doctors have been advising me to do so."

He went on: "Over the last two years, it has been an uphill struggle to keep on top of my job and to do it as well as I would have liked.

"I have also had to have further medical treatment during the Christmas recess, which will continue into the New Year.

"I therefore feel this is an appropriate moment to hand over to Andrew."

Aberdeen-born Mr Raffan came to Holyrood from a journalistic background, starting off as a freelance journalist in the early 1970s and becoming a Sunday Express diary columnist in 1976.

Party tribute

In 1981 he became a parliamentary correspondent and sketch writer with the Daily Express.

He was a Tory MP in North Wales for nine years from 1983, and in the 1990s worked as a TV presenter and interviewer for HTV Wales.

Scottish Lib Dem Leader and Deputy First Minister Jim Wallace said: "Since his election in 1999 Keith Raffan has been a strong parliamentary performer, particularly in the chamber where he has led for the party on crucial issues such as the war in Iraq and on European and international affairs.

"As well as holding a number of important positions within the party, Keith has been a tireless campaigner for patients suffering from Hepatitis C and drug misuse."

Travel claim

When the breakdown of MSPs' expenses was released, Mr Raffan insisted that �41,154 of his total was a backlog for travel covering three years.

The presiding officer said: "I have spoken with Keith Raffan and respect his decision to resign.

"Keith has brought intelligence and sparkle to the parliament since he became a member in 1999."

Under the procedure for replacing a list MSP, Mr Reid notifies the returning officer of the vacancy and the returning officer responds with the name of the next person on the Lib Dem list who is willing and able to serve.