British Gas owner Centrica has fuelled further controversy after reporting profit rises.
It reported a two per cent rise in UK and Ireland operating profits to £906 million, helping group operating profits jump four per cent to £1.5 billion.
The company is expected to face fresh calls to address tariffs for businesses and domestic consumers.
Centrica's British Gas residential energy supply arm, which only covers UK homes, reported an 11% drop in operating profits to £553 million, compared with £623 million in 2015, but said the reduction was due in part to a customer exodus.
More than 409,000 UK home customers left the business in 2016, marking a 3% fall to 14.25 million.
British Gas announced it was extending a price freeze on its standard energy tariff until August, "despite increases in external costs", but customers are expecting prices to soar later this year, following the Brexit-induced collapse of the pound and rising wholesale energy prices.
The industry has faced increasing pressure to treat loyal customers fairly and has been criticised for being slow to pass on falls in wholesale gas prices, with consumer groups hitting out at the size and timing of cuts.
British Gas will extend a price freeze for customers on its standard energy tariff until August.
Mark Hodges, head of British Gas' owner Centrica, said: "We're pleased to give our customers on standard tariffs the peace of mind that the price they're paying will remain unchanged until August.
"We are determined to give our customers great offers and services. In December we promised to take tangible action to improve how the energy market works for all our customers. That effort continues.
"We aim to do even more in the coming months to meet our customers' needs, earn their business, and reward their loyalty."
However ScottishPower customers were not so fortunate as the company announced a 7.8% rise in standard gas and electricity bills following "rises in energy wholesale markets and compulsory non-energy costs."
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Britain's biggest residential energy supplier British Gas has reported a sharp increase in profits for 2015.
Energy group Centrica confirmed a 31% increase in operating profits at its British Gas residential arm at £574 million last year.
However, wider group underlying earnings at owner Centrica fell 12% to £1.46 billion.
Operating profit the previous year was at £439 million.
Earlier this month, the company announced it is cutting 500 jobs saying it had to be competitive in a "fast-changing" energy market.
British Gas has announced it is cutting 500 jobs.
The job losses will be hitting its loft and cavity wall insulation business, as part of the company's efficiencies programme.
Brian Strutton, national officer of the GMB union described the announcement as "a real sickener".
The jobs are part of 6,000 cuts announced by owner Centrica last summer, with the group saying it had to be competitive in a "fast-changing" energy market.
Mark Hodges, chief executive, energy supply and services, UK and Ireland at British Gas said the company was focused on improving its efficiency and effectiveness.
"British Gas is well positioned to grow, but we must ensure that our costs allow us to be competitive for our customers."