Centrica said an 11% rise in profits at Scottish Gas residential came after last year's colder-than-normal weather saw gas use leap 12% and in spite of a 1% fall in customer accounts to 15.7 million in 2012.
The results are likely to raise questions over the fairness of energy bill increases after Scottish Gas raised tariffs by 6% for around 8.4 million households at the end of last year.
Group adjusted operating profits rose 14% to £2.7 billion, but Centrica said it paid more than £1 billion in tax and invested £2.7 billion in 2012.
Directors from the company appeared on television this morning to defend the results.
Chris Jansen, managing director of services and commercial at Centrica, said a colder winter last year contributed to the rise in profits.