Charities have warned that some of the most vulnerable households could miss out on the £400 to help with soaring energy bills this autumn, after details were revealed of how all homes in Great Britain would receive the support. The money, part of the already announced energy bills support scheme, will be paid in six monthly instalments of £66 or £67 to about 29 million households. Charities and campaigners raised immediate concerns that more than 2 million prepayment meter customers could have difficulties accessing the support. Those who pay by direct debit will receive an automatic deduction off their bills, while those with “smart” prepayment meters will see an automatic monthly top-up added to their account. However, customers with older “non-smart” prepayment meters will not receive the support automatically, instead receiving an energy bill discount voucher each month via text, email or in the post. Customers will then have to redeem these in person at their usual top-up point, such as newsagents or post offices. Those using prepayment meters include some of the country’s poorest and most vulnerable households who are finding the soaring cost of energy and other bills most difficult. Maureen Fildes of the fuel poverty charity National Energy Action said she was fearful that some people using prepayment meters may struggle to get the vouchers. “There is a lot of fear about how people are going to survive the winter,” she said on BBC Radio 4’s Today programme. “I don’t think that is going to be sufficient to help people cope with the cost of living this winter. “A lot of people on prepayment meters don’t have a lot of interaction with the energy supplier; they just top up as and when they need to. If it’s a paper voucher, we’d like to ensure that people don’t ignore post from their supplier. It’s not going to be another bill; it is going to be some level of support.” She urged people to ensure that their contact details with their supplier were up to date and not to ignore any post from their supplier. More than 4m households use prepayment meters in Britain, according to the energy regulator, Ofgem. Less than half of those meters – 1.9m – are smart devices that will allow this payment to be made quickly and easily. Kwasi Kwarteng, the business and energy secretary, said: “People across the country are understandably worried about the global rise in energy costs, and the pressure this is placing on everyday bills. Advertisement “While no government can control global gas prices, we have a responsibility to step in where we can, and this significant £400 discount on energy bills we’re providing will go some way to help millions of families over the colder months.” It comes days after households were warned average annual energy bills could hit £3,850 from January, triple the level at the beginning of this year. The chancellor, Nadhim Zahawi, said the discount was “part of our £37bn of help for households, including 8m of the most vulnerable households receiving £1,200 of direct support to help with the cost of living”. The announcement comes after the consumer champion Martin Lewis said the prime minister and the Tory leadership contenders, Liz Truss and Rishi Sunak, needed to agree on a package to help consumers. He said Boris Johnson’s “zombie government” was failing to address the crisis caused by rising energy bills and warned that decisions on support could not be delayed until Johnson’s successor was in office. Lewis, the founder of MoneySavingExpert.com, said households would start receiving notice of increased bills before the Tory leadership contest concluded, with the energy price cap rising to £3,500 or more in October.