Energy giant Npower will scrap 1,460 UK jobs as part of a major restructuring programme which will see some jobs outsourced to India.
The utility, which is owned by German electricity company RWE, said the move enables the business to focus on delivering a more "efficient, flexible and improved" customer experience.
Npower currently employs a total of around 11,000 people across the UK with 9,500 in its retail business, meaning the cuts represent 13% of the company's overall workforce and 15% of its retail business.
"I understand that these changes would be incredibly hard for some of our employees and we'll be doing everything we can to support them over the next few months," said Paul Massara, chief executive officer of Npower.
He added: "This restructure is necessary if we are to deliver the levels of service our customers deserve. All calls would still be answered in the UK."
The employer also disclosed that over the next right months Npower's offices in Stoke on Trent would close, affecting around 550 employees.
In addition, the company said one of Npower's three offices in Oldbury would close and around 400 employees would be made redundant.
The energy giant said there would also be a number of redundancies at npower's sites at Rainton Bridge, Sunderland (affecting around 430 employees, subject to consultation) and in Leeds (affecting around 80 employees).
Npower's site in Thornaby would close but all roles there would be secure and relocate to our Northern head office in Rainton.
The company stressed there would be transport support for these employees for three years.
The decision will see much of Npower's customer facing work being outsourced to Capita.
The company said around 540 Npower workers would transfer to Capita under Transfer of Undertakings (Protection of Employment) Regulations and work alongside its current teams.
Under the proposals, Npower back office administrative activity, including checking meter readings against customers' bills, will be outsourced to India using Tata Consultancy Services.
The move follows an announcement by RWE earlier this month that the firm planned to cut 6,750 jobs across Europe.