British Gas boss Chris Weston is quitting the energy supplier to become chief executive of temporary power firm Aggreko, leaving a widening gap in the senior ranks of owner Centrica.
His departure comes as the firm faces political pressure on household bills and a squeeze on profits.
Centrica is also facing the loss of finance director Nick Luff by the end of the year and strong speculation that chief executive Sam Laidlaw is to leave.
Loading article content
The group has been buffeted by public anger over bills and is facing a full-scale competition inquiry into the energy sector.
Earlier this month, Centrica said it would leave energy tariffs unchanged this year despite revealing that group profits will be lower than expected.
Earnings from its residential energy business dropped 6% to £571 million last year due to rising wholesale prices and a milder winter.
The firm lost more than 360,000 gas and electricity customers in 2013 as households switched to rivals.