Around two million long-term savers with Standard Life will see their payouts reduced after the insurer today became the latest to cut final bonuses as stock market values plummet.
The Edinburgh-based life and pensions giant said it was also introducing stricter penalties for policyholders who want to cash-in their pensions and investments early.
The group is introducing so-called market value reductions (MVRs) to more with-profits plans and hiking others that already exist, up to 30% in some cases.
It blamed the recent hefty falls in equity markets seen amid the global financial crisis and economic slowdown.
The FTSE 100 Index has lost around a quarter of its value since August as spooked investors have headed for the exit. Today's changes will typically reduce the maturity value of a pension by between 9% and 12% and between 11% and 13% for endowment values.
The final bonus changes will mean that, for example, an investor who had paid £50 a month into a pension for 20 years would see the value of their transfer value fall from £83,874 last November to £78,609 today.
Someone who paid an initial investment of £10,000 into a with-profits bond at the end of October 2005 would see their cash-in value reduce from £11,462 last October to £9,828 today.
Standard Life said: "Investment returns have generally been poor over the last year, but particularly so since August, resulting in today's decision to reduce final bonuses and extend MVRs.
"The changes that we have made today will ensure that we maintain fairness between planholders who choose to leave with profits and those who remain invested until their plan maturity or retirement date."
The regular bonuses paid on the policies will remain unchanged, it confirmed.
With-profits investments are long-term savings policies that hold back some returns in good years and pay out in bad ones. The policies are often taken out as pensions or endowments to pay off a mortgage.
Legal & General has already cut its final with-profits bonuses earlier this month, by up to 9% on average, while Norwich Union also this month re-introduced MVRs across its unitised with-profits plans.