The energy regulator has highlighted a doubling in the gap between what customers are paying for electricity and gas and suppliers' costs over the past 12 months.
Ofgem figures indicated average net margins more than doubled between October 2012 and October 2013 from £45 to £95 per household on a rolling month-on-month basis, while wholesale prices rose by just 1.7%.
The wholesale cost - what energy firms pay to generate electricity and produce gas - has been cited by the firms as a core reason for the recent spike in household bills by an average 9% ahead of this winter.
The so-called big six companies collectively made profits of £3.7bn in 2012.
But energy industry sources insisted each company's costs were complicated by when energy was bought - often two years in advance to ensure supply.
Firms employ varying hedging strategies - essentially financial bets on wholesale prices - in a bid to limit their exposure to the trend of sharply rising prices.
Bosses of the big six are due to appear before the House of Commons Energy and Climate Change Committee on Tuesday to explain hikes in bills that many politicians have claimed will force people to chose between "heating and eating".
The average energy bill breakdown. Pic: OfgemThe Prime Minister's official spokesman said that it was up to the companies to justify their charges to consumers.
"It is for the energy companies to explain the decisions they have taken around bills to their customers," the spokesman said.
In a statement, Ofgem said it "has been at the forefront of making the energy market more transparent for consumers over the past few years".
It added: "Our own weekly monitoring published on our website estimates that, over the last year, the cost of wholesale gas and electricity to serve a typical dual fuel customer would have risen by around £10 to £610.
"However, this figure could be higher depending on the hedging strategy of an individual company for buying gas and power in forward markets.
However, it also pointed out that wholesale costs were now rising for this current winter - by 8% for gas and 13% for electricity.
Nevertheless, its analysis of the wholesale costs versus profit margins sparked an immediate backlash from the industry while Platts, a provider of energy industry information, suggested near-term energy costs were at a record high during the summer.
Energy bills and the battle for the consumer has sparked a febrile game of political brinkmanship since Ed Miliband announced Labour would freeze prices for two years at the party's annual conference.
David Cameron responded by announcing last week that he would roll back green taxes, which account for £112 of the average fuel bill each year.
Labour's Ed Miliband has pledged to freeze energy bills for 20 monthsThe Liberal Democrat response has been furious, given environmental issues played high on the Liberal Democrats' election manifesto, and they have refused to give ground on green levies. However, Nick Clegg has yet to suggest an alternative.
Simon Hughes, the deputy leader of the Liberal Democrats, has suggested a rebate of £50 on energy bills for low-income households be included in the Chancellor's autumn statement.
Chief Secretary to the Treasury Danny Alexander suggested the Liberal Democrats would be willing to shift some of the burden of the levies - which cost households an average £112 a year - from energy bills to general taxation.
Labour's shadow energy secretary Caroline Flint called for a rethink of the biggest levy, the Energy Companies Obligation (ECO), which she described as expensive, bureaucratic and failing to reach those who really need it.
The ECO scheme operated by the big six power companies adds £47 annually to the average bill to pay for energy-efficiency measures like insulation and new boilers for households in fuel poverty.
A report by the IPPR think tank suggested that 1.3 million of those in greatest need have not received help because £434m - 80% of the total £540m budget - was being targeted at homes that are not fuel-poor.
Labour has pledged to "reset the market" if it wins the next election and freeze bills for 20 months - a policy Mr Cameron has described as a "con."
He has pointed to growth in smaller competitors in the market - insisting there is value in switching now the big six have some rivalry.
Speaking at an event at the Mini plant in Oxford, Mr Cameron said: "I'm frustrated about the big six. I want to see the big 60, I want to see many more energy companies.
"Since we came to office, there have been eight new companies come in and start in terms of selling electricity and gas. That's helping competition."
One of those companies, Co-op Energy, said today that it had tripled customer numbers in a year.
The fledgling gas and electricity supplier, which recently called on larger rivals to put customers before profits, saw its total six monthly sales increase seven-fold.
It raised its tariffs by 4.5%, half the rate of its bigger competitors.