Close to two million energy vouchers - designed to help those on prepayment metres afford their bills - are sitting unclaimed as fears grow that cash-strapped homes are missing out on vital extra help.

Since October every household in England has been given extra money each month under the Energy Support Scheme - that will total £400 by the end of March - to lessen the impact of rising gas and electricity prices.

While homes with energy contracts have had direct debit payments discounted or money sent back to their bank accounts, customers with prepayment meters have been sent extra help in the form of vouchers or codes that need redeeming when they top-up their meter.

But close to five months into the scheme and it has emerged that more than 1.9 million vouchers - totalling more than 100 million in extra help - still sit unused with many of those having now expired before being cashed-in.

While January saw the biggest amount of vouchers used so far since the scheme's launch last year - as under pressure energy companies work to reach vulnerable homes - the government wants to see more done to ensure the money available is spent.

Energy Security Secretary Grant Shapps explained: "The help we’ve put in place means we are covering around half of most household’s energy bill this winter - this is an unprecedented level of support.

"With January temperatures having dropped to as low as -10 degrees in some parts of the country, I am pleased to announce today a record numbers of households taking up the government support.

"But many households are yet to redeem the vouchers they are entitled to and I want energy companies to redouble their efforts to get the support to those who need it."

The use of prepayment meters by often the most vulnerable in society has come in for fierce criticism in recent weeks following claims that debt agents were breaking into people's homes to force-fit meters.

As a result, forced prepayment meter installations have been suspended by energy watchdog Ofgem while it investigates and consults on whether rules need to be changed.

In terms of voucher uptake, it is London and the south east where the most amount of vouchers sit unused with only 58% and 69% of vouchers having been claimed respectively.

Redemption rates in all other regions are now edging above 70%, although ministers are maintaining calls for communities, local leaders and suppliers to make sure households using traditional prepayment meters are aware of the support and how to access it.

How to redeem your vouchers

No household has needed to apply for the energy payments, they're automatic, but how you receive the money will depend on how you pay for your gas and electricity.

The extra help was £66 for October and November and is £67 per month from December through to March when the scheme will then close.

Customers using prepayment meters should be in receipt of vouchers - either in paper form or by text - and these can be redeemed at a Post Office or PayPoint.

With uptake struggling, and the focus on the use of prepayment meters for those most likely to struggle, energy companies are obliged to make several attempts to contact people who haven't cashed in the vouchers which have been sent to them.

How long do they last?

Vouchers, says consumer organisation Which?, will last for 90 days after which they expire.

This means that the vouchers sent for October and November are no longer valid while December's vouchers will be the next to run-out - on March 8 - if not cashed-in soon.

However, energy suppliers do have the power to reissue expired vouchers, which are then renewed for a further 90 days to allow them to be used.

What if they've expired?

Anyone who has expired codes or vouchers should get in touch with their energy supplier as soon as possible to request an extension to their vouchers while being sure to use new vouchers as they then come in.

But all vouchers - explains Which? - must be used by June 30 2023.