The group confirmed Iain Conn's departure alongside an announcement that it would exit the production of oil and gas as it targets further cost savings.
Centrica chairman Charles Berry said: "Iain has led the strategic repositioning of Centrica since 2015 and has been the driving force behind our plan to turn Centrica into a sustainable business that is built around delivering clean, affordable energy and high-quality services and solutions for our customers, and to respond to the significant global challenge of moving to a lower carbon energy future.
"Iain has now agreed with the board that, while he will continue to focus on driving this transformation, including pursuing the announced divestments and continuing to drive performance and efficiency, he will also support an orderly succession before stepping down in due course."
Conn faced criticism from unions in April for his 44 per cent pay rise in the same year the company announced job cuts affecting up to 4,000 people.
Centrica said today that it would now target an even larger cost reduction, aiming for £1 billion annualised efficiencies over the 2019-2022 period, up £250 million on previous estimates.
This will be achieved through the refocusing of the portfolio on to customer-facing services, but the company also said it had identified more opportunities for savings, including right-sizing its management structure and reviewing its property footprint.
Meanwhile, Centrica said it would rebase its dividend due to the "challenging environment" in the first half of the year.
The interim dividend was slashed by more than half to 1.5p per share, while the full-year expected dividend was rebased to 5p per share.
Accounts showed the company swung to a statutory pre-tax loss of £446m in the six months to 30 June, compared with a £704m profit this time last year.
Adjusted revenue dropped 2 per cent to £13.8bn, while underlying earnings fell 19 per cent to £1.08bn.
Centrica said it had been affected by the UK energy price cap and increased demands on its cash flows, including additional pension contributions.