Holyrood standards watchdog Dr Jim Dyer has claimed he was put under undue political pressure in his final year.

In his last annual report after two terms in office he has said his successor should be made more independent by not having to apply for a second term, and insists that independent legal advice is the cornerstone of the role.

He told The Herald last night: "Independence is a crucial aspect of the role."

In his report, Dr Dyer claimed: "When the parliament, early on in its life, chose a method of dealing with conduct complaints, it laid great store by having an independent investigator but there are at times pressures that potentially constrain that independence.

"In my report I have encouraged my successors to be vigilant to protect the independence of operation, which is central to public confidence in the commissioner role. As a recent high-profile investigation demonstrated, independent legal advice is an essential component of the commissioner's independence."

Dr Dyer was forced to spend more than £18,000 on legal costs last year, on matters including the investigations into former Labour leader Wendy Alexander's campaign donations.

He said complaints over the past year added to the total bill, which was almost three times higher than in 2005-06.

He said: "The increased legal costs for 2007-08 reflect the complexity of complaints going to stage-two investigation during the year, including a high-profile case."

Dr Dyer referred to legal challenges and highlighted insufficient guidelines.

The legal bill for 2007-08 was £18,416 compared with £11,468 the previous year and £6,794 in 2005-06.

Dr Dyer said 23 complaints were lodged.

He considered 19 of the complaints but took forward just three between April 2007 and March 2008.