British Gas, the biggest energy supplier in the country, reported on Thursday that its adjusted operating profit for 2013 came in at 571 million pounds (950 million U.S. dollars), down 6 percent compared with the previous year.
British Gas also saw a 2-percent drop in customers in 2013 as households switched to other suppliers following its move to increase tariffs by 9.2 percent on average from last November.
The company attributed the results to "the pressures that British Gas and the wider industry were under last year with the competing demands of securing supply, reducing carbon emissions and keeping energy affordable."
"Following a strategic review last year, we are now firmly focused on providing our customers with excellent service, leadership in digital smart homes, and good value products," said Chris Weston, Managing Director of British Gas.
The energy giant has been under pressures from both customers and politics. Earlier this month, British Gas's prices and profits were questioned by Energy Minister Ed Davey, who suggested the firm might have to be broken up.
"I think the reputation of Britain as a place in which to invest is under threat and the time to correct that is now not after the 2015 election, by which time the possibility of the lights going out in Britain will be looming much larger," said Rick Haythornthwaite, chairman of Centrica, the parent company of British Gas.
British Gas is the Britain's leading energy supplier, and serves around 12 million homes in Britain - nearly half the country's homes - as well as providing energy to one million businesses.