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.

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 cheaper rivals.

British Gas increased tariffs by 9.2% on average from November as part of a painful round of winter bill rises across the industry. But a shake-up of the Government's so-called green levies on bills saw it pass on a 3.2% reduction.

The company has been singled out amid political pressure on the industry, with Energy Secretary Ed Davey highlighting its dominance in gas supply earlier this year.

He urged competition authorities to 'think radically' in their inquiry into the sector, which could see the former nationalised monopoly firm broken up.

Mr Weston took charge of British Gas last year following the departure of Phil Bentley. Mr Bentley was not directly replaced, with Mr Weston, boss of Centrica's US retail arm, instead taking responsibility for all so-called 'downstream' operations.

He was paid a basic salary of £553,000 last year, with a total package of £1.3 million. His new role at FTSE 100-listed Aggreko will see him receive a basic salary of £750,000.

Centrica said he was subject to 12 months notice and a further announcement would be made in due course about the timing of his departure.

Mr Laidlaw said: 'Chris has made an important contribution to Centrica over 11 years, leading a number of our businesses, in the UK and North America.

'We will be sorry to see him leave, but recognise that Aggreko offers a great opportunity for him.'

Aggreko said Mr Weston was expected to join next year 'once he has completed his commitments at Centrica'.

He said: 'Aggreko is a fascinating business and I'm very excited to be taking on this role. I have watched and admired Aggreko's tremendous growth over recent years.'