Around 1.6 million pension pots worth almost £20 billion remain unclaimed by savers in the UK, according to research by the Association of British Insurers (ABI).
A survey of 12 large insurers, covering around half of the defined contribution pensions market, found 800,000 lost pension pots with an estimated worth of £9.7bn.
Scaling this up to the whole market, ABI estimated that unclaimed pensions could total around £19.4bn, or nearly £13,000 per pot.
This is higher than previous estimates by the Department for Work and Pensions, which said there were around £3bn in lost pension pots in 2010.
Yvonne Braun, director of long-term savings and protection at ABI, said the research highlights the "jaw-dropping scale" of the problem, and urged the Government to take forward the pensions dashboard.
Kate Smith, head of pensions at Aegon, added:
"It's notoriously difficult for people to keep track of small pension pots, particularly at the beginning of their working life.
"Saving for retirement needs to be made as simple as possible and the launch of the pension dashboard will hopefully help people to keep track of their pensions, with the additional bonus of seeing all of them, including the state pension, in one place."
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