A cash-strapped NHS board has agreed to write off a £90,000 salary overpayment that was mistakenly given to one member of staff over eight years.

NHS Lothian will not claw back a sum worth nearly five nurses’ salaries, after legal advice suggested the move would be unlikely to be successful.

Miles Briggs, Scottish Conservative shadow health secretary, said: "This avoidable error is a total waste of taxpayers’ money which is particularly frustrating at a time when the NHS is so starved of money and staff. All NHS boards must ensure mistakes like this do not re-occur and the SNP must properly resource our health service.

“This case just demonstrates once again the financial mismanagement of NHS Scotland at the hands of this incompetent SNP Government.”

NHS Lothian has an annual budget of over £1bn, employs 26,000 staff and provides health services to around 800,000 people.

The organisation has struggled in recent years to hit waiting times targets and has paid the private sector for spare capacity.

Between April and June last year, figures showed that NHS Lothian missed outpatient targets on nearly 15,000 occasions.

This was in spite of a Scottish Government treatment time guarantee of 12 weeks, which has been put on hold across Scotland.

Further questions have been raised about NHS Lothian’s financial stewardship after a sizeable sum of money was paid to a single employee in error.

A February minute of the body’s audit and risk committee alluded to the mistake and the obligation of recovering taxpayers’ money, but few details were provided.

However, the next meeting of the same committee revealed that the gross amount was £87,858, which came to around £57,000 after tax.

According to the document, NHS Lothian chief executive Tim Davison said the overpayment had resulted from a “simple arithmetic calculation error”.

The minute noted that, while most overpayments are recovered within one year, it could take over 50 years to recover the sum in this case.

NHS Lothian’s executive team concluded that no action would be taken for several reasons, including that an “error” had been made in the original payroll calculation.

Routine budgetary control measures did not identify the mistake for years, and a further error was made in advising the employee that no repayment would be required.

The minute added that the board had never “deducted without consent” and there was a risk of court action by the employee. It explained: “Legal advice was that the Board has a less than 50% chance of success.”

Regarding the option of withholding future pay awards and uplifts from the unnamed individual, NHS Lothian heard there was no precedent for this either and would run a “significant risk of a breach of contract claim”.

The committee agreed that NHS Lothian was at fault and decided to write off application to the Scottish Government, which approved it last week.

In 2015, it was reported that NHS boards had paid almost £1.7m in wages to staff who had already moved or left their jobs.

The mistakes, which covered a three-year time period, included NHS Lothian paying £658,640 to ex-staff. Greater Glasgow and Clyde, Tayside and Grampian paid out more than £130,000 each year over the same period.

Susan Goldsmith, director of finance at NHS Lothian, said: “In cases of overpayment, the default position for NHS Lothian is always to recover salary overpayments, even if the individual has left the organisation. This was an isolated and exceptional case and was the result of human error.

“There is a need to balance the requirement to ensure value for money for the taxpayer with the duty to be a fair employer. This error occurred a number of years ago and robust systems have since been put in place to prevent a similar situation.”