British Gas owner Centrica is axing 5,000 jobs, representing 20 per cent of its global workforce.
The group, which employs over 27,000 people and has over three-quarters of its workforce based in the UK, is undergoing a major restructuring amid the Covid-19 pandemic.
Over half of the job losses are expected to come from management teams and follow 4,000 cuts planned by this year which were announced in 2018.
Centrica said half of its 40-strong top-brass leadership team would be stepping down from their posts and the company by the end of August, with plans also in the pipeline to strip out three other layers of management to help streamline the business.
All in all, around half of the jobs lost will be in the group's corporate, management or leadership teams.
Centrica, which is embroiled in a huge cost cutting drive, hopes to trim £2billion of its outgoings by 2021.
The group has furloughed around 3,800 of its workforce during the pandemic, but they remain on full pay.
Chris O'Shea, the company's chief executive, said: 'The harsh reality is that we have lost over half of our earnings in recent years. Now we must bring focus by modernising and simplifying the way we do business.'
He added: 'I truly regret that these difficult decisions will have to be made and understand the impact on the colleagues who will leave us.
'However the changes we are proposing to make are designed to arrest our decline, allow us to focus on our customers and create a sustainable company.'
The GMB union vowed to fight the cuts, with spokesman Justin Bowden saying: 'A combination of the (energy price) cap and too little, too late management decisions have left a once proud brand crippled and weak.
'Slashing thousands more jobs is not the answer. You cannot just cut your way out of a crisis.
The majority of the restructuring is expected to take place in the second half of this year, following consultation on the proposals with affected staff.
Significantly for Centrica staff based in the UK, the group said: 'In addition to the proposed new organisational design, the company will today start consultation to simplify terms and conditions for employees in the UK.
'Centrica has over 80 different employee contracts, each with multiple variants, with many of the agreements dating back over 35 years. We need to modernise these to enable us to best serve the changing expectations of today's customers while retaining the quality of our services.'
The company has seen the pandemic curb energy demand and has had to adapt to a price cap imposed in 2019 on the most common energy tariffs in Britain.
Earlier this year it canceled its dividend for 2019 and warned of an increase in non-payments by customers.
It said its latest restructuring push would lead to fewer customer-facing business units and that the job cuts could come as soon as the second half of this year.
A spokeswoman for Centrica said it was unable to disclose the locations for the proposed job cuts as they were subject to consultation, but said roles across all divisions of the firm would be affected.
Although it is still by far the biggest energy supplier in Britain, British Gas has been squeezed by increased competition in recent years.
The company has lost around half its earnings in the past decade, as smaller suppliers chipped away at its market share, from a quarter in 2013 to 19 per cent today.
The rise of smaller suppliers was capped off last year when Ovo Energy, which was only founded in 2009, bought SSE.
Last month Ovo announced that it would axe 2,600 roles at the combined business, as the coronavirus pandemic sped up its restructuring plans.
Centrica's share price is firmly in the red this afternoon and at the time of writing was down 3.28 per cent or 1.37p to 40.46p, having dropped over 4 per cent earlier. A year ago, the now FTSE-250 listed group's share price stood at around the 93.88p mark. The company has recently been relegated from the FTSE 100 index on the London Stock Exchange.
Last week, Prime Minister Boris Johnson admitted there will be 'many job losses' exacerbated by to the pandemic as businesses suffer losses during lockdown.
A 'significant' number of the near 9million employees currently enrolled on the Government's Job Retention Scheme e are being warned they could be made redundant as the months roll on.
The furlough scheme has closed to new applicants and from August, bosses will have to start contributing to workers' pay.