Up to half a million of the UK’s most vulnerable families have been left without government help to pay their energy bills since October, with around 1.3million vouchers for homes with prepaid meters lost, delayed or unclaimed.

Charities and MPs call on ministers to intervene, Labor says the government has been warned “repeatedly” that those using prepayment meters are not getting enough support.

Households missed around £80million in government aid in the two months since the scheme was launched, with around 1.3million vouchers left unredeemed, according to the Guardian’s analysis of data from the complementary company PayPoint and the Department of Business, Energy and Industry. Strategy.

All households in the UK are due to receive £400 this winter under the energy bill support scheme, which Rishi Sunak announced in February when he was chancellor. Since Russia’s invasion of Ukraine, energy prices have soared, pushing inflation to its highest level in 41 years, causing hardship for millions as cold weather s ‘installed.

Families who pay by direct debit will receive a credit to their account each month from October to March, without having to do anything. But the 2 million homes with traditional prepaid meters – typically the poorest households in the country – should automatically receive a £66 voucher from their provider in the post, which can be used when recharging.

However, charities are sounding the alarm, saying many homes have not received vouchers. Readers who contacted the Guardian said they had made several requests to their energy suppliers to receive vouchers and, in some cases, were still waiting.

A mother in London said the delays left her unable to heat her home for weeks as mold grew in her 12-year-old son’s bedroom. Other readers in London, Carlisle and Sunderland said they spent hours on the phone with their energy suppliers trying to find out where their vouchers were. Others living in homes that have been divided into studio apartments, each with its own sub-meter, said separate households were forced to share a voucher.

A quarter of the vouchers expected for the first months of the scheme have not been claimed, according to PayPoint, which handles top-up payments for around 750,000 households and shops across the UK. PayPoint said October refunds were 75% and November refunds were 63%.

According to separate government data released last month, 2.1 million vouchers were to be delivered to households. Extrapolating PayPoint data, this suggests that 500,000 households that should have received government assistance did not receive or redeem their voucher in October, and 760,000 withdrew in November. A total of 1.3million vouchers worth £84million have gone unclaimed since the scheme began.

The vouchers will expire three months after issue, which means that the October vouchers will be invalid from January 3, while the November ones will expire on February 5.

Gillian Cooper, energy policy manager at Citizens Advice, said: “We’re concerned that people using prepaid meters – who risk ending up in cold, dark houses if they don’t top up – could miss their vouchers. »

Ed Miliband, the shadow secretary of state for climate change and net zero, said the government should step in to ensure poorer customers don’t pay more for energy.

“The government has been repeatedly warned that too many households using prepayment meters are not getting the support they deserve with their energy bills. Yet successive Prime Ministers have failed to tackle this problem,” he said. “With the cost of living soaring, the Government must end once and for all the unfair penalty premium imposed on users of prepaid meters, as Labor has repeatedly called for.”

Matt Copeland, head of policy and public affairs at the charity National Energy Action (NEA), said the government had been warned the voucher scheme risked depriving thousands of households of support. “Unfortunately, we saw that coming,” he said. “We knew from experience that this would happen. Not enough has been done to ensure we have a better outcome.

Copeland said he thinks some people using prepaid meters may have saved the vouchers until it gets colder. However, he said the scheme was little known and customers of prepayment meters were more likely to be indebted to energy companies. They might therefore be reluctant to open letters that look like bills and are therefore missing.

The NEA said 8.4 million households could be in fuel poverty from April, when the government’s separate energy price guarantee, which caps the cost of gas and electricity, takes effect. end. In his November budget, the Chancellor, Jeremy Hunt, announced that the guarantee would increase from April to £3,000 a year for the typical house.

The NEA has called on the government to fund reductions in permanent charges for prepayment meters, regardless of usage. Permanent charges can cost around £200 per household, depending on the region.

Steve O’Neill, Corporate Affairs and Marketing Manager, PayPoint, said: “We are still seeing a higher redemption rate on November vouchers than those issued in October, although all vouchers have a validity period. of three months. People are advised to use their oldest vouchers first, to reduce the risk of them expiring compared to newer vouchers. If an eligible person has not yet received their voucher, they should contact their energy supplier as soon as possible.

Energy UK, the supplier lobby group, has advised customers with traditional prepayment meters to check registered contact details and seek out all supplier communications. The program does not apply to people with prepayment smart meters connected to the Internet.

A spokesperson for Energy UK said: ‘Suppliers are working hard to ensure their vouchers reach customers and will make repeated attempts using the channels and contact details available to them. Although there may be different reasons why a number of vouchers have not yet been redeemed, we seek to help raise customer awareness of the support available by working with outlets like PayPoint and Post Office and groups of consumers like Citizens Advice.

A spokesperson for the sales department said: “All Energy Bill Support Scheme vouchers for October and November should have been dispatched by suppliers. If customers have not received them or are having difficulty exchanging them, they should contact their supplier.

“Suppliers must ensure vouchers reach customers by the 11th working day of the month, and they are working with the Post and PayPoint to mitigate postal strikes. Customers can also speak to their supplier if they need a voucher reissued.