Plans by energy giant npower to cut 2,400 jobs in the UK amid heavy financial losses have been described as a "devastating blow" to its workers.
The company, owned by German group RWE, ended days of speculation by confirming that its 11,500 strong workforce will be reduced by almost a fifth.
The two main RWE businesses in the UK made an aggregate loss of £154 million in 2015 - £99 million at npower and £55 million at RWE Generation.
The job cuts will affect a mixture of direct and indirectly employed staff.
A two-year recovery plan was announced to deliver a "robust business" built on lower costs, simplicity, high-quality customer service, and ready for the challenges of the future.
A statement said: "Npower takes its responsibilities to its employees seriously and will consult fully with affected employees and with unions over its proposals for the future of the business."
Unison general secretary Dave Prentis said: "These huge job losses will come as a devastating blow to the workforce.
"Npower has been in trouble for some time thanks to poor decision-making at the very top, and workers are now paying the price. The company's failure to invest properly in new systems has left it with one of the worst customer service records in the business."
Paul Coffey, chief executive of RWE npower, said: "Npower results continue the trend seen earlier in 2015, but they are nonetheless extremely disappointing and we are starting a two-year process to fix them.
"They show a business that tried to do too much, too soon, while not focusing enough on the fundamentals in a constantly changing market. This led to over-complicated processes and procedures resulting in unhappy customers, too many complaints and extra costs to put things right.
"These issues are not insurmountable. Over the past few months, we have looked at every part of npower, and over the next two years we're fundamentally changing how the company operates.
"We shared the outcome of this review yesterday with employees. By 2018, around 2,400 fewer people will support npower overall through a mix of those who work directly and indirectly for npower."