The taxpayer is paying at least £300,000 a year for a health board's three chief executives - one seconded, one suspended and one standing in for the other two.

Under questioning by MSPs yesterday, Dr Kevin Woods, chief executive of NHS Scotland, described the situation at NHS Western Isles as "undesirable and unusual".

Scotland's most senior health service official was giving evidence before Holyrood's audit committee which is investigating the board's debt of £3.64m. It follows years of turmoil within NHS Western Isles, punctuated by allegations of financial mismanagement, bullying and harassment.

In 2006, a management task force was sent to take control. The move resulted in the departure of the then chairman David Currie, chief executive Dick Manson and the medical director Dr John Smith.

The appointment in January last year of Laurence Irvine as chief executive of NHS Western Isles, was supposed to herald a new dawn for the health board's fortunes. But he was suspended in September on full pay of around £100,000 a year. It is understood this followed a freedom of information request from within the board for the CV presented by Mr Irvine with his application.

He was replaced by John Turner, former chief executive of Borders Primary Care Trust.

Dr Woods told the committee that Mr Manson had sought a secondment in 2006 and was Director of National Development Projects.

Mr Manson was still paid by the health board, but NHS Scotland reimbursed it for his salary. Mr Irvine was paid by the board while Mr Turner was paid directly by NHS Scotland.

Dr Woods said that Mr Turner and the health board's new chairman John Angus Mackay appeared to have got things under control and expected to balance their budget or report a small surplus in the financial year just about to end.

Dr Woods, who is due to visit the board in Stornoway next month, said Health Secretary Nicola Sturgeon was aware of the position. "I am concerned. The issue is what are the options available to me. I have to operate within the framework of employment law."

Mr Manson had not been subject to any disciplinary action by NHS Western Isles when he had sought secondment. "There will have to be discussions between the board, Mr Manson and ourselves about his future," he said.

SNP's Willie Coffey told Dr Woods: "When Mr Manson and Mr Currie took up their posts, the Western Isles was actually in surplus, but when they left there was a deficit approaching £3.5m. For the chief executive to then be moved sideways, promoted or otherwise is going to seem incredible."