Energy firms need to work harder to identify and protect poor and elderly customers, an independent report found.
The study’s authors were told of incidents in which vulnerable people were either left in the dark or facing bills running to thousands of pounds.
In one case, a disabled woman with poor mental health had her electricity cut off.
Energy UK, which commissioned the report, called for new rules of conduct.
The trade association, whose members include energy suppliers and generators, set up the Commission for Customers in Vulnerable Circumstances last year, to look at how standards of care could be improved.
In its report, the commission said energy companies, regulators and the government were failing to consistently meet the needs of customers.
Commission chairman, the Labour peer Lord John Whitty, said: “From listening to those on the front line, it’s very clear that there are huge variations in the way energy suppliers deal with those in need.”
He said those examples ranged from “really good practice” to cases of “seriously insensitive” treatment that “fall far short of acceptable”.
“It can’t be right that in such a highly-regulated industry, it can be a matter of chance how – or if – you get the support required.”
‘Intimidating and harassing’
Evidence provided to the report’s authors by Citizens Advice included an account of one man, who was suffering with multiple mental health issues, facing a bill of £1,900.
Citizens Advice said the man felt his energy provider, which was not named, was “intimidating and harassing” him to pay the bill even though he could not afford it.
In another case, a pensioner was overcharged by £1,000 after her electricity meter broke.
The Commission for Customers in Vulnerable Circumstances report called for an independently-monitored code of conduct advising companies on how to improve the way they deal with poor, elderly and disabled customers.
It said energy companies needed to train staff to help them to identify and offer support to vulnerable households.
Firms should also make sure customers can contact them on a free phone number and by letter, it said.
The report went on to recommend that the regulator, Ofgem, should ensure energy firms had measures in place to protect those customers.
In addition, the report’s authors called on the government to introduce a state-funded scheme to help tackle fuel poverty.
A spokesperson for the Department for Business, Energy and Industrial Strategy said: “This Government strongly believes that everyone has the right to a reliable and reasonably-priced energy supply, and wants to protect consumers from rip-off deals.
“This is why we are making sure two million low-income households get money off their winter energy bills, as well as protecting 11 million households with our energy price cap. We are also giving extra money to pensioners through the winter and are committing £6 billion to upgrading the energy efficiency of the homes of the most vulnerable.”