British pensions are among the worst in all of the European Union countries.
While pensions in Germany, Denmark and Poland rose in value, nearly 10% has been lost on British pensions since the year 2000.
A new report blames high charges and inflation for the poor performance.
Pensions in Britain have not grown as fast as the cost of living, says the report from Better Finance, an agency which lobbies the EU on consumer issues.
It noted that many different fees are levied against British pension, many of them taken surreptitiously. The UK’s high inflation, greater than elsewhere in the EU, has also impacted negatively on pensions.
The study was the first to compare "real" returns, after inflation, earned by savers across Europe.
Better Finance, which is funded by the European Commission, compared fund growth, after fees, with cost of living increases.
The real value of UK pension pots dropped by an annual average of 0.7% since the millennium. So, £100,000 invested in 2000 would buy £90,634 worth of items today, a loss of nearly 10% of the value.
In Denmark, by contrast, the same £100,000 sum would have grown to £192,778 in today's money, Better Finance calculations showed, while German personal pensions returned 2.2%, making £100,000 worth £135,617.
The worst pensions were Italy and Spain. Spanish pensions dropped 1.2% a year in real terms, turning £100,000 into £84,500 worth of spending money.
Gina Miller, founder of the True & Fair Campaign on charges, said hidden fees in Britain had conspired to keep growth below inflation.
She said the Better Finance report "burnt down the image that the pensions industry has the public's interest at heart" and called for it to be "disinfected".
"The scandalous hiding of charges has to end sooner rather than later."
An Office of Fair Trading report last year found some company pension policies charged as much as 2.3% a year, eroding a heft amount of investment growth.
The report's authors said they were "surprised" by the lack of transparency in Britain.
