Families could be thousands of pounds better off in retirement if they claimed little-known pension top-ups from the taxman while they take time off work for childcare.

While a parent or carer is looking after children and not earning, a partner or relative can pay into their pension for them, gaining 25 per cent top-ups on those contributions from HM Revenue & Customs.

This is because pensions contributions get tax relief at the 20 per cent basic rate of income tax — if you pay in £800, it is topped up to £1,000, giving you an effective 25 per cent boost on your savings. This applies even if you are paying in to someone else’s pension.

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The maximum you can pay into a pension for a non-earning partner is £3,600 a year, which would cost you £2,880 before tax relief — the government would add £720. A one-off top up of this amount at age 30 could be worth almost £4,000 in a pension by the time you are 65. The scheme was introduced in the 2001 Finance Act under the Blair government.

Some 63 per cent of parents were not aware of the pension top-up scheme, according to a survey of 1,000 parents by the financial platform Octopus Money. Of those who did not know about the perk, 65 per cent told Octopus that they would have used it if they had been aware.

Some 34 per cent said they had reduced, paused or entirely stopped contributions to their pensions while they were out of the workplace caring for children.

Last month the ONS reported that mothers lose an average of £65,000 of earnings in the first five years after having a child.

And while the pension pots of men and women in their twenties are roughly equal, by ages 55 to 60 men have about 40 per cent more than women, according to an Octopus analysis of its customer data.

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Some 42 per cent of the women who responded to the Octopus survey said that they were not confident they would have enough money to retire comfortably, compared with 28 per cent of men.

More than half (52 per cent) of parents said their finances were hit harder than expected when they had children. But while childcare costs remain a significant burden, 45 per cent of parents said their biggest worry was saving for their children’s future.

Ruth Handcock, the chief executive of Octopus Money, said: “As a working parent who has experienced parental leave twice I empathise with those families who want to celebrate the joy of having children without compromising on their financial security for later life.

“I strongly urge all new parents to think about financial planning in parallel with family planning, to futureproof the whole family, not just the newest member.”