Labour is calling on ministers to ban the forced installation of prepayment meters on financially stretched households until at least spring.
He pressed for the ban to last “at least three months” to help those struggling to pay their bills to stay warm during the colder months.
The former Labour leader, in a separate statement, labelled the forced imposition of prepayment meters (PPM) as “shameful” and said it was time to “halt this scourge of blackouts by the back door”.
Mr Miliband’s intervention comes after Citizens Advice said an estimated 3.2 million people across Britain ran out of credit on their prepayment meter last year — the equivalent of one every 10 seconds — because they could not afford to top up.
Hundreds of thousands of properties have been forcibly switched over to more costly PPM after bill-payers failed to keep up with rising energy payments.
Smart meter users have found their accounts switched remotely to PPM while others have been confronted at their door by teams sent by energy companies — armed with magistrates’ court warrants — to physically make the change.
Campaigners say those switched often then go without power as they cannot afford to keep the meter topped up — something that is referred to as “self-disconnection”.
It comes after energy bills have soared due to rampant inflation and the impact of Russia’s invasion of Ukraine.
Mr Miliband said: “It is shameful that forced installation of prepayment meters is cutting off people’s heat and power, including some of the most vulnerable people in our society.
“We need immediate action to halt this scourge of blackouts by the back door.
“Labour is calling for a moratorium to stop even greater misery this winter, while the Government, regulator and energy companies get a grip on this problem, to tackle the hardship millions are facing.
“Rishi Sunak must not blame others for what is his Government’s dereliction of duty.
“He is standing by while families across the country are being cut off.”
As well as the ban on forced switches to PPM, Labour is calling for an urgent review into how energy vulnerability can be reduced.
It also wants to put an end to the “unfair penalty” that PPM customers face by committing to additional support for them, Mr Miliband’s letter said.
The End Fuel Poverty Coalition has previously suggested that magistrates’ courts have been “rubber stamping” warrants to install meters in properties where customers might be struggling to pay their bills.
The coalition pointed to a freedom of information request revealing that 187,000 applications were made by energy companies in the first six months of 2022.
Those with smart meters have found they have been switched remotely to more costly PPM plans by their energy supplier, Ofgem has previously confirmed, with 60,000 alone switched between August and October.
End Fuel Poverty last year called on ministers and Ofgem to ban switching customers to a PPM under warrant and prohibit switching smart meters to PPM mode without “active, informed, consumer consent”.
Ofgem stipulates that certain groups such as disabled people and those with long-term health conditions should not be forced on to a prepayment meter.
But Citizens Advice has previously raised concerns to the watchdog and the Government that it had seen evidence of suppliers forcing people in these groups on to prepayment meters.