A third of pensions don't qualify for new rules which allow savers to withdraw their entire pension pots, it's been reported.
The investigation by the Daily Mail found as many as six million policies could be "hard to cash in", including 2.29m final salary pensions.
More than half that figure is public sector pensions, while insurance companies which hold three million pension pots won't let savers use them like bank accounts because of the structure of their contracts, many of which are several decades old.
Others prevented from withdrawing their savings include some who were sold pensions by doorstep salesmen in the last three decades of the 20th century, many of which have either high early exit fees or require customers to pay a financial adviser sums of up to £2,000 before they can withdraw their savings.
However, chancellor George Osborne said yesterday that 60,000 people had already withdrawn £1bn from their pension pots - an average of £17,000 each.
"While the number of people taking money from their pensions has not significantly increased, the way they are doing so has, with less than one in 10 people currently choosing to buy an annuity, compared to eight or nine in 10 only a couple of years ago," said Tom McPhail, head of pensions research at Hargreaves Lansdown.
But the Financial Conduct Authority told the Daily Mail it has already begun a review of the new rules.
"The majority of people have been able to take advantage of the new rules without any problem, but we are talking to those firms where issues have arisen," it said.