THE head of Scotland's new single fire service has received an eye-watering £600,000 boost to his pension pot within months of starting his job, the Sunday Herald can reveal.

Alasdair Hay, 51, whose £165,000 salary is more than the Prime Minister's, enjoyed the 40% hike after becoming chief officer of the Scottish Fire and Rescue Service (SFRS) in October 2012, the service's first accounts disclose.

The total value of his pension pot, known as the Cash Equivalent Transfer Value (CETV), leapt from just over £1.4 million to more than £2m between March 2012 and March 2013. His predicted annual pension also leapt from just under £60,000 to £88,000 in a year.

Hay's deputy chief officer, Alex Clark, who earns £135,000 a year, enjoyed a boost to his pension pot of £177,000 up to £925,000. His future pension rose from £55,000 to £70,000.

The accounts cover the period when the SFRS was operating at a shadow level ahead of its official launch in April, and include five-and-half months when Hay was chief officer.

The SFRS said the increases reflected changes in the pair's wages, but MSPs have queried the sums.

Scottish LibDem leader Willie Rennie, who warned against merging the fire and police services, said: "People will be astonished that senior public-sector staff are getting such generous increases while so many others are still facing real pressures on the cost of living.

"The increase in the pension pot for one individual is enough to staff a whole small fire station."

Tory chief whip John Lamont said: "The public will be stunned to see the amounts of money being given to senior management here. They were sold the move to a single service on the grounds it would save money."

The SFRS came into being in April with a budget of £290m following the merger of Scotland's eight regional fire services. Scotland's eight police forces merged at the same time to become Police Scotland.

Hay's pension hike followed a series of changes to his salary as a result of reorganisation.

A firefighter for 30 years, he was paid £88,600 as deputy chief fire officer at Tayside Fire and Rescue, then from May 2011 to January 2012 he was seconded to the Scottish Government, where he was paid the equivalent of £99,500 a year.

Hay was then appointed acting chief fire officer of Tayside on April 1, 2012 on £110,500, but left on October 15, 2012 to become chief officer of the SFRS on a £165,000 salary.

The fire service has a history of controversy over pensions, with several chief officers taking generous retirement deals then being immediately rehired in their old jobs.

In one case, Strathclyde Fire and Rescue Service was last year criticised for "systemic failures" after its board approved the retirement of chief officer Brian Sweeney, allowing him to take a huge lump sum, then rehired him a month later on a £150,000 salary.

A SFRS spokeswoman said: "Both the chief officer and the deputy chief officer of the new SFRS are members of the defined benefit final salary Firefighters' Pension Scheme.

"The pension increases outlined reflect increases to their individual accrued pension rights as a result of increases of salary and their additional accrued service since the last audited accounts were published.

"The value of their respective pensions is based on their pensionable pay and length of service."