Energy suppliers accused of failing vulnerable customers ahead of winter have been named and shamed by regulator Ofgem.
The watchdog reviewed 17 energy firms in total as part of its review, with each supplier told they need to improve their practices.
There are only 23 energy suppliers still trading, after a wave of them collapsed last year.
Five companies - Good Energy, Outfox, So Energy, Tru Energy and Utilita - were found to have "severe weaknesses".
The report found "moderate weaknesses" at E (Gas & Electricity), Ecotricity, Green Energy UK, Octopus and Shell.
And seven others - British Gas, Bulb, EDF, E.ON, Ovo, Scottish Power and Utility Warehouse - had shown "minor weaknesses".
As part of the review, the firms had to explain how they identify and keep records of vulnerable customers - and whether they had been added to a priority register.
The Priority Services Register makes sure extra help is available to people who need it, including advance notice of power cuts.
Energy suppliers also explained to Ofgem whether they were offering free gas safety checks, if they were supporting vulnerable customers on prep-payment meters, and if they were providing appropriate information to customers.
Ofgem's director of Retail Neil Lawrence said: "From eligible customers who are missing out on free gas safety checks through to companies not identifying vulnerable customers to be offered obvious support on the Priority Services Register, this robust review has highlighted that suppliers need to do more to support consumers.
"We welcome the cooperation from suppliers and action taken so far, and, although we are seeing some very good practice in parts of the industry, we can see there is still much more to be done."
He said that "most suppliers" take their responsibility to protect vulnerable customers seriously but added: "We've seen a number of failings across the board which need to be urgently addressed.
"It's going to be a very challenging winter for everyone and customers must be confident they are getting the help and support they need.
"My message to suppliers today is simple - be proactive. Help your customers to know what support is available, and then deliver it."
Simon Oscroft, co-founder of So Energy, said: "Over the course of the last months and weeks, we have provided Ofgem with extensive additional information related to this review and we are disappointed that Ofgem has proceeded on the basis of incomplete information, and in a manner that may now cause vulnerable customers unnecessary concern.
"For the avoidance of doubt, So Energy has never switched a smart meter-equipped customer from credit to prepay without their knowledge and consent, and has an approach to customer vulnerability that is in line with our caring and honest values."
Utilita said: "Ofgem's report does not represent where we are as a business today, nor does it acknowledge the significant progress we have made - and are making - since its initial assessment in early summer.
"As such, we look forward to seeing Ofgem's updated report in the near future."
Nigel Pocklington, CEO, Good Energy said: “It is disappointing that once again Ofgem have published a verdict part way through the evidence-gathering process. Despite providing Ofgem with extensive information which addressed their concerns, it is regrettable that this publication does not account for this.
“Good Energy has an excellent record of taking care of vulnerable customers - including being independently assessed before joining Energy UK’s Vulnerability Commitment which aims to continually improve support - and we will be considering our actions off the back of this report.”
Rocio Concha, Which? director of policy and advocacy, said: "It's hugely concerning to see Ofgem has found that so many energy firms are falling short on the support they provide to their most vulnerable customers.
"Energy firms must urgently up their game and do everything they can to support their customers through this crisis, especially those most in need."
How the energy firms ranked
‘Severe’ weaknesses
- Good Energy
- Outfox the Market
- So Energy
- Tru Energy
- Utilita
‘Moderate’ weaknesses
- E (Gas & Electricity)
- Ecotricity
- Green Energy UK
- Octopus
- Shell
‘Minor’ weaknesses
- British Gas
- Bulb
- EDF
- E.ON
- Ovo
- Scottish Power
- Utility Warehouse