British Gas parent Centrica will run the gauntlet of public outrage when it unveils a near-50 per cent hike in annual profits at its residential arm today.

The bumper £554 million haul - 46 per cent ahead of 2008 - comes just weeks after hefty winter fuel bills dropped on to millions of doormats across the country.

Industry watchdog Ofgem said this week that energy firms have boosted margins by £30 for each typical dual fuel customer in the last three months as wholesale energy costs fall.

Gary Smith, national officer at the GMB union, said: “Buying cheap and selling dear will always add up to high profits in a natural monopoly. No great managerial elan or skills are needed.

“It is long overdue that the Government should step in and take control of the energy sector and put in place proper plans for secure supplies at reasonable prices as happens in the rest of Europe.”

Centrica is also expected to hike its dividend to investors bringing total payouts for the year to around £650 million. The dividends offer returns to major institutional holders such as pension funds.

British Gas - the UK’s biggest energy supplier with around 16 million customers - became the first of the “big six” to cut gas prices recently.

Centrica will also argue profits have recovered from an abnormally low level in 2008 when the group waited until late in the year before passing on soaring wholesale gas prices.

The 2009 figures for the overall group will also show operating profits down 7 per cent to £1.82 billion in 2009 due to dwindling returns from its production business.

This is because lower wholesale gas prices have a bigger downward effect on production profits than the boost given by the residential business.

While British Gas will also have gained from last month’s snow - which falls outside the period of the results - figures from rivals have suggested that any boost from December could be offset by an unseasonably mild October and November.

The UK’s second largest utility group, Scottish & Southern Energy, said its customers used on average around 5 per cent less gas and 4 per cent less electricity between October 1 and January 31 compared with a year earlier. This also reflects home insulation measures by households.

Analysts say British Gas could turn up the heat on its rivals later this year with more price cuts after securing its current position as the cheapest in the market.

Morgan Stanley’s Bobby Chada said: “Given the weak commodity price environment, Centrica will have scope for further tariff cuts later in the year and still meet consensus expectations.”