Nicola Sturgeon has seen a six-figure fall in the headline value of her ministerial pension pot after her officials were found to have miscalculated it for years.

Previous Scottish Government accounts stated the former first minister had a pot worth almost £500,000 by the end of March 2022.

However the latest accounts have slashed that by almost £120,000 after it was discovered the value had been overstated by around a third.

An obscure note buried in the 194-page document admits the figure was “revised due to previous incorrect aggregation” of various types of entitlements.

Instead of her separate roles over time as a cabinet secretary and first minister being treated sequentially, they were wrongly combined, inflating the apparent value of her pension.

The mistake only came to light after Ms Sturgeon stood down as first minister in the spring and her pension entitlement was fully reassessed.

After the Herald on Sunday asked about the issue, the Scottish Parliament and the Scottish Government initially each said the other was responsible.

However the Government agency involved finally said the value of Ms Sturgeon’s pension had been “adjusted to its proper value” after the error was discovered.

Ms Sturgeon, 53, announced her resignation as FM in February and formally stood down at the end of March after SNP members elected Huma Yousaf as party leader.

She has since struck a deal with publishers Pan Macmillan for her memoirs, with an advance understood to be between £300,000 and £350,000, meaning she is not short of funds.

She also has a salary of £67,662 as the MSP for Glasgow Southside.

However the drop in her headline pension value appears significant.

The Scottish Government’s consolidated accounts for 2021/22 said the worth of her pension, known as cash equivalent transfer value (CETV), was £495,000 at the end of March 2022.

But the consolidated Government accounts for 2022/23, which came out last week, showed the CETV at 31 March 2022 had been cut to £377,000, a drop of £118,000 or 24%.

Ms Sturgeon’s CETV at 31 March this year was given as £434,000, a level that previous versions of the accounts wrongly suggested she had already passed in 2020. 

The latest accounts also revised down Ms Sturgeon’s accrued pension due at the age of 65,  from a projected £30,000 to £35,000 a year to £25,000 to £30,000.

They state: “Nicola Sturgeon’s Cash Equivalent Transfer Value (CETV) at 31 March 2022 has been revised due to previous incorrect aggregation of Cabinet and First Minister salaries on which the pension figures were based. As there is a significant difference in salary between these roles, pension is now calculated separately according to policy.

A spokesperson for the Scottish Public Pensions Agency said: “The pension figures in the 2022/23 Scottish Government consolidated accounts are correct. 

“The cash equivalent transfer value (CETV) of the former First Minister’s parliamentary pension has not reduced, it has been adjusted to its proper value. 

“When Ms Sturgeon stepped down as First Minister, care was taken to calculate the value of her pension entitlement under the scheme rules. 

“During this process, it was identified that CETVs for previous accounting years had been calculated using her combined service as an office holder and First Minister, whereas the scheme rules require entitlement during these periods to be calculated separately. 

“This was the first occasion that the pension entitlement of a retiring First Minister had been tested under the specific scheme rule, and the correct figure is now included in the Scottish Government accounts.”

Ms Sturgeon declined to comment.