Campaigners have called for action amid reports a growing number of households on smart meters are being cut off by energy companies.
A rise in the so-called 'switch by stealth' of people being forced onto pre-payment meters has been branded "alarming" amid calls on energy watchdog Ofgem to intervene.
Ofgem has said it has received reports of vulnerable customers being left without power for days or even weeks.
It has told suppliers they must address the issue "urgently", warning companies it will not hesitate to "take action" if failings are found in how energy companies have operated.
Before smart meters, if a household fell behind on energy payments, companies would have to request a warrant to enter a household to install a prepayment meter.
These meters are essentially a pay-as-you-go arrangement: once the credit is used, a household will be disconnected and left without electricity or heating.
However, if a household has a smart meter, energy companies can now disconnect them remotely without having already installed a prepayment meter.
Smart meters monitor the electricity a household uses, and automatically send readings to energy companies - providing more accurate bills and clarity about the energy you're using as you use it.
They also provide energy companies with a mechanism to switch direct debit payments to a prepayment system without a warrant.
According to data from Ofgem, more than 152,000 households with smart meters were remotely switched to more expensive prepayment plans for gas or electricity last year.
But Citizens Advice has predicted that 450,000 people could be forced onto a prepayment plan this winter - with 180,000 of them expected to be remote switches via a smart meter.
The charity also told the BBC that, so far in 2022, almost 500 people have been in contact in distress after being forcibly moved onto prepayment - a 158% increase in cases on 2021.
In October, the price comparison website Uswitch said it had seen a "worrying" increase in the use of prepayment meters, reversing a long-term downward trend.
Simon Francis, co-ordinator of the End Fuel Poverty Coalition, urged the government and Ofgem to protect customers from being switched by "stealth".
"In a time of crisis, moving people onto more expensive pre-payment meters without their express permission is unacceptable," Francis told Yahoo News UK.
"That smart meters are now being used to make this switch by stealth is even worse.
"Energy firms have an obligation to help those in financial difficulty and the government and Ofgem must step in to ensure that they are delivering on this."
National Energy Action director of policy Peter Smith said the reports are "alarming".
“It is really alarming to hear the number of customers being switched from their smart meter to prepayment meters," he told Yahoo News UK.
"There is no excuse for poor customer engagement or leaving people at risk of disconnecting themselves from supply."
A spokesperson for the department of energy, business, and industrial strategy (BEIS) said: “We expect suppliers to fully comply with their obligations and welcome the steps Ofgem is taking.”
It comes amid the worsening cost-of-living crisis, with the average yearly energy bill reaching £2,500 in October - a record high, and almost double the price it was last year.
And energy bills are set to rise again in April, with estimates the average yearly bill could hit £3,500 per year.
Campaigners are urging the government to honour their pledge to uprate benefits with inflation in the autumn statement next week, warning millions of low income households are already being forced into destitution without more support.
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