It marks a 6% drop on the £606 million the year before but is unlikely to calm public anger over rising energy costs.
Centrica said British Gas shed 2% of residential customer accounts in 2013 to 15.3 million as households switched to other suppliers following its move to increase tariffs by 9.2% on average from November as part of a round of painful winter bill rises across the industry.
It added that another 100,000 had quit the group so far this year, but customer switching was now "stabilising" after it scaled back its price rise by 3.2% following a shake-up of the Government's so-called green levies on bills.
Across the group, operating profits were 2% lower at £2.7 billion last year.
Chief executive Sam Laidlaw admitted that public and investor trust in the energy industry had been "damaged" by the threat of price controls and political intervention.
He attacked Labour leader Ed Miliband's pledge to freeze tariffs if the party wins power, saying it was "not a credible solution".
He said: "We firmly believe that any form of price control in a competitive market is not the answer and is not in the best interests of customers, and this has been clearly demonstrated by experience in other markets.
"Such proposals create both short-term uncertainty for all energy suppliers and longer-term additional costs for customers," he added.
The group's shares have plunged by more than a fifth since autumn following Labour's price freeze pledge, with the stock driven down further after Energy Secretary Ed Davey recently called for a full-scale investigation into the energy market that could see British Gas broken up.
In a letter, Mr Davey urged competition authorities to "think radically" as they consider whether to launch a probe.
Centrica's results showed that higher wholesale prices and unseasonally warm weather at the end of last year saw British Gas suffer an 18% slump in operating profit in the final six months of 2013, which offset a better start to the year.