British utility group Centrica said Thursday that its net profits plunged 78 percent last year, hit by a large one-off charge, weak economic conditions, mild weather and higher wholesale gas prices. Earnings after tax slumped to £421 million (497 million euros, $662 million) in 2011 from £1.94 billion the previous year, Centrica said in a results statement. The fall was mostly due to an £844-million charge on the revaluation of contracts, pension changes and losses on disposals. However, adjusted operating profit, or earnings before interest, taxation and depreciation, edged one percent higher to £2.42 billion, just short of the £2.48 billion expected, according to analysts polled by Dow Jones Newswires. Revenues added two percent to £22.8 billion. Milder-than-expected weather in Britain last year and the poor economic climate pushed profits lower at the group\'s domestic British Gas division, despite hikes in domestic electricity and gas prices. \"2011 was a tough year, both for Centrica and our customers,\" chief executive Sam Laidlaw said in the statement. \"But the strength of our integrated business and balance sheet means we\'ve been able to take the lead in helping customers through these difficult times, as well as delivering growth and making the investments on which Britain\'s energy future depends.\" The results update came one day after Centrica agreed to buy oil and gas assets in the North Sea from French peer Total for $388 million (292 million euros) in cash.