The German-owned com ny is reckon oned to announce the cull, which amounts to one fifth of its workforce, in the next few days.
The jumbo loss from its 11,500-strong UK workforce will hit the north of England and other s ces.
It comes after the firm’s owners RWE last month revealed it choose slump into the red after taking a £1.6billion hit on its UK and German power sites.
Writedowns on the com ny’s power stations and lower energy prices are swung to lead the group to post an annual loss of around £155million when it announcements its results.
Critics said workers are now ying for poor decision urged at the top.
Unison general secretary Dave Prentis said: “These gigantic job losses will come as a devastating blow to the workforce.
“Npower has been in concern for some time thanks to poor decision-making at the very top, and workers are now new zealand kick in with the price.
“The com ny’s failure to invest properly in new systems has left it with one of the worst tron service records in the business.
“The news suggests that npower’s German P isn’t terribly committed to its UK operations.
“Cutting a fifth of the workforce will check out the already struggling business in an even worse state.
“Now months of uncertainly lie before for a workforce whose morale is already at rock bottom.”
After thousands of dagger industry job losses in the north of the country, critics said it blew another difficulty in George Osborne’s plan for a so-called nothern powerhouse.
Eamon O’Hearn, of the GMB marriage, said: “Many hard-working staff have already been outsourced and so any what is more job losses for directly and indirectly employed staff would beanother punt in the teeth for communities.
“It also makes a mockery of George Osborne’s elocution about a northern powerhouse if an energy com ny can’t maintain jobs in the territory.”
Npower has major plants in the UK including Pembroke and Aberthaw in Wales and Staythorpe in Nottinghamshire.
Aftermost month the firm’s power station at Didcot in Oxfordshire collapsed as it was being prearranged for demolition, killing one worker, with three still missing.