UK enegry consumers have faced ever-rising bills as the Big Six maintain their profits (Reuters)

The so-called Big Six energy firms that dominate the UK's consumer-facing market saw a 77% leap in average profit per-household from 2011 to 2012, the industry regulator has revealed.

Ofgem, the energy watchdog, said supplier profit per household lifted from £30 to £53 between the two years. Firms' profit margin for supply for household customers more than doubled from 2.8% to 4.3% over the same time period. A cold winter in 2012 lifted energy consumption in Britain.

It comes amid attacks by anti-fuel poverty campaigners on the industry's biggest players that they are profiteering by squeezing consumers as hard as they can to get the most money out of them at a time when Britons' incomes are falling in real terms.

"Making a profit is not an entitlement," said Ofgem's report. "It should be earned by suppliers gaining and retaining customers, offering competitive prices, the right products, and good customer service. How efficiently suppliers run their businesses also determines the profits they make.

"Our analysis in 2011 showed that the way in which the whole retail market worked meant there was not as much competitive pressure on suppliers as there should be."

Energy UK, the lobby group which represents the consumer-facing energy industry, hit back at Ofgem's report.

"Ofgem's report sets out the earnings before tax paid for supply side and for generation," said Energy UK.

"The figures do not take into account the costs of the huge investment the energy companies are making, the interest or the tax they are paying. These are not net profit figures.

"Ofgem supports what the companies have been saying. The main reasons customers have seen their household bills go up is because the cost of gas and electricity have gone up as well as other add-ons, such as the social and environmental policies, rising fast.

"Earnings from generation pays for major investment the industry is making. The generation figure of earnings before interest and tax of 20% is not, as Ofgem acknowledges, 'a meaningful measure of profitability'. Energy UK is therefore asking Ofgem to use the much more meaningful figures of cost of capital."

The body concluded: "The industry is committed to transparency and openness. We ask others to use clear explanations that cannot be easily misunderstood."

Suppliers have been lifting their gas and electricity bills by several percent, causing much public outcry. They say it is a response to higher wholesale energy costs as well as the expense of investment in the country's dated infrastructure and a passing on of green taxes. Critics say they are simply bolstering their profits.

Ofgem's report was released ahead of protest groups, including UK Uncut and Fuel Poverty Action, holding demonstrations against energy providers Npower and British Gas over the rise in energy prices.

UK Uncut said more than 1,000 demonstrators are expected to take part in the protests in London.

The anti-austerity groups plan to march on Npower offices with a coffin filled with bills.

In addition, protests will be taking place in Oxford at the new British Gas headquarters as well as Lewes and Bristol.