The Department for Work and Pensions has recalculated the impact of the government plan to switch to the Consumer Prices Index for increasing pension payments. According to DWP, the estimated cost of the switch from the Retail Prices Index to CPI for members of private sector pension schemes has ballooned by about £10bn to £85.9bn.

It means people in private sector pension schemes will lose out - either through lower increases to pensions in payment, or lower increases to deferred pensions, or both.

The DWP estimates that 20% of private sector schemes will increase pensions in payment in line with CPI. It also estimates that 80% of schemes will increase deferred pensions in line with CPI until pension age.

"This is a massive attack on workers' pension rights," said Prospect pensions officer Neil Walsh. "The original Budget decision to link social security and public sector pension increases to CPI was clearly a stealth attack on benefits, designed to raise significant amounts of money without people realising the true impact.

"Extending the attack to cover private sector schemes will result in a massive transfer of wealth from scheme members to shareholders."

He stressed that millions of workers and pensioners across both the public and private sectors would lose many thousands of pounds as a result of this switch.

• Join the 1st March lobby of parliament protesting at the switch to CPI, and write to your MP to protest. See the CSPA website. There are also draft letters in CutStop resources.