Final salary pension scheme members could see a 4% cut in benefits after the BoE used miscalculated inflation rates for more than a decade, experts say.
The BoE last week admitted it had underestimated clothing prices used to determine inflation by 5.5% between 1997 and 2009, meaning the consumer price index rate should have been 0.3% higher than published.
It also admitted the error was "likely to have a larger impact on RPI inflation than on CPI inflation".
Investment managers predicted the error in clothing price collection could have shaved 4% off a pensioner's final salary entitlement.
BDO Investment Management actuarial director John Broome Saunders says: "Had the inflation calculation been done correctly, many final salary scheme members would now find themselves entitled to a pension around 4% higher than their actual entitlement.
"This does not just affect pensioners; deferred scheme members have also been denied a similar level of increase."
Pension schemes inflate members' benefits in line with CPI or RPI measures. However, pension experts say the admission did not mean inflation figures would change retrospectively.
Hargreaves Lansdown pensions analyst Laith Khalaf says: "This highlights the fact both CPI and RPI are measures of inflation rather than inflation itself.
"They are never an accurate reflection of an individual's inflation rate.
"People in final salary schemes all have different inflation rates depending on their consumption, so the inflation linking is ever only an approximation of price increases."
The BoE revealed the miscalculation in its February inflation report. It said it had scaled down the impact of clothing import prices when collecting prices, reducing the CPI rate.
For the future, the BoE said would to use a more sophisticated collection method to take better recognition of clothing import prices.
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