Hundreds of thousands of households have not redeemed vouchers which will take £400 off their energy bills this winter.

PayPoint said only a little over half (53pc) of the 800,000 vouchers it has issued have been redeemed so far.

It means that households are so far missing out on around £27 million in support that would be paid by the government.

Under the government scheme, which was announced in May, households will get between £66 and £67 taken off their energy bill every month between October and April.

For households that pay via direct debit, or who have smart pre-payment meters, this money is taken off automatically.

But millions of households are on older pre-payment meters – and these people are instead sent a voucher which they have to redeem in a shop.

In data first reported by the BBC, PayPoint said it has emailed vouchers to the customers of nine different energy companies, but it is not the only company that will be issuing them so the problem is likely to be larger.

The business said many of the 28,000 convenience stores where customers can top up their gas and electricity cards are open seven days a week.

It said the most popular times to redeem the vouchers are between 11am and 1pm on Saturdays and Sundays.

Adam Scorer, chief executive of the charity National Energy Action, said: “One of the least surprising outcomes from the Energy Bills Support Scheme is that people on older pre-payment meters are most likely to miss out.

“They may not know that the scheme exists, be reluctant to open letters from suppliers, miss the email, or can’t print the voucher off.

“Having the support in place is, of course, vital. Making sure people can and do access it is just as important.

“The UK government must learn this lesson for whatever comes after the Energy Price Guarantee.”