Ofgem has questioned the "Big Six" energy firms' claims that soaring bills are down to a rise in wholesale market prices of gas and power, the Financial Times reported.
The energy regulator's figures claim that wholesale prices increased by only 1.7% over the past year, which should have been reflected in a rise of only around £10 on bills.
Centrica argued that Ofgem's methodology is '"flawed".
Energy UK have issued a warning that "no-one should be cold this winter" and urged people to contact their energy company if they have failed to deliver insulation improvements in time to homes.
A statement said:
No-one should be cold this winter. If people are worried they should contact their energy company - they may have schemes to help and can offer advice.
Energy UK has been working with local authorities on the delivery of the ECO and the Green Deal. We have already held a number of roadshows round the country where participants - including local authorities, housing associations, providers, DECC and the Green Investment Bank - have been able to share their experiences and learn for best practice.
We appreciate that ECO, like any major new Government programme, takes time to bed in and for people to understand how things work, but the industry is committed to helping in that process.
The Local Government Association have warned that tens of thousands of poor and elderly people will face another winter of high bills and cold homes because of the failure by energy companies to deliver insulation improvements in time.
The organisation, which represents 373 councils in England and Wales, urged the companies to work with local authorities to get the work done.
Energy companies are collecting this money through a levy which is contributing to the cost of fuel bills and they have an obligation to invest it as swiftly and effectively as possible to deliver upgrades which save vulnerable people money and keep them warm and healthy this winter.
Councils understand their communities and are uniquely well placed to pinpoint the areas where upgrades will do the most good. Local authorities up and down the country stand ready to work in partnership with the energy companies to make sure the hundreds of millions of pounds of unspent money is used to deliver warmer homes and lower bills to the people who need it most.
Energy companies are falling behind in their obligation to pay for insulating the homes of tens of thousands of poor and elderly people, council leaders claimed.
An analysis released by the Local Government Association suggested that the power giants are more than 60% behind their target to deliver more energy-efficient homes.
This is despite raising almost £1 billion so far this year through the Energy Company Obligation (ECO) levy, which adds around £50 to the average household's annual bill.
The ECO is designed to raise money to deliver warmer homes for people on limited incomes and lower their utility bills by reducing the amount of energy they need to use.
In response to an inquest that found neglect was a contributing factor in the deaths of five elderly residents at the Orchid View Care Home in West Sussex, a Department of Health spokesperson described the lack of care as "appalling".
They added: "We have made it clear that there must be a sharper focus on taking tougher action when things go wrong and holding those responsible to account.
"Confidence in the regulation regime has been shaken, but we have now turned a corner."
A coroner ruled that neglect contributed to five of the 19 deaths that occurred at Orchid View care home in Copthorne, West Sussex.Read the full story ›
The daughter of a woman who died due to neglect at Orchid View care home said her mother was denied the "dignity and compassion" she deserved and called for "dramatic changes" to the care system to ensure that there are consequences for care home owners for "substandard services."
Speaking outside the court, Linzi Collins, whose mother Jean Halfpenny overdosed on a blood thinning drug whilst in the care home, said:
"The horrific details that have emerged about Orchid View are beyond comprehension. How the corporate failings of Southern Cross could create these events and how such terrible standards could go unnoticed by the authorities for so long has left us baffled.
"In this day and age you expect measures to be in place to protect vulnerable members of society from being subjected to such horrendously poor care.
"Our mum deserved to be treated with dignity and compassion but Orchid View failed to provide her with even a basic level of care, despite being paid a significant amount of money to do so
"We believe dramatic changes are needed to the current care system, starting firstly with greater accountability for care home owners if they are found to be making unnecessary mistakes and offering substandard services."
Lisa Martin, a former care home worker who alerted police to failing at the Orchid View care home in Copthorne, said she the "final straw" for her came when she was told by a nurse that 28 drug errors had been made on just one night shift.
She called police who arrived the next day.
The coroner said 19 residents at Orchid View suffered "sub-optimal" care. All of those residents died from natural causes, she ruled. But five of those died from natural causes "which had been attributed to by neglect", Ms Schofield ruled.
They were Wilfred Gardner, 85, Margaret Tucker, 77, Enid Trodden, 86, John Holmes, 85, and Jean Halfpenny, 77.
Speaking outside the inquest, Lisa Martin, who first informed police of the problems at the care home, said she felt she had no choice but to come forward:
I came forward because I had witnessed too much poor management and care to vulnerable adults and I couldn't live with the knowledge any longer and felt I had no choice but to tell the police.
Morally I know I did the right thing but personally I have not worked for two years and the case has had a huge impact on my life.
However, I wouldn't want to dissuade people from doing the right thing if they see vulnerable elderly people being abused and neglected.
Speaking of her former colleagues, she added: "They shouldn't be allowed to work in the industry."
Penelope Schofield, the West Sussex coroner, said:
There was institutionalised abuse throughout the home and it started, in my view, at a very early stage, and nobody did anything about it.
This, to me, was from the top down. It was completely mismanaged and understaffed and failed to provide a safe environment for residents.
Ms Schofield said it was "disgraceful" that the home was allowed to be run in the way it was for around two years. She criticised the Care Quality Commission (CQC) which gave Orchid View a "good" rating in 2010 - a year before it shut.
I question how this could be the case and I question whether the inspection that did take place was fit for purpose.
It's a heart-breaking case. We all have parents who will probably need care in the latter part of their lives.