Tata Steel has announced that proposed cuts will affect mainly management and administrative roles at sites in Scunthorpe, Teesside and Workington.
David Hulse, national officer of the GMB union, said the news had been a surprise.
"This terrible news has come straight out of the blue. It is a shock to the workforces in Scunthorpe, Workington and Teesside.
"GMB is bitterly disappointed as earlier this year we saw 1,000 people leave the company and everyone involved has worked hard to make all-round improvements.
"GMB will insist on no compulsory redundancies and to bring the number of job losses down."
More top news
Film stars including Kelly MacDonald and Jessica Hynes are in the Lake District this evening for the world premiere of Swallows and Amazons
Emma Jesson brings you Sunday night's forecast
It was the 10th visit from the youngsters, who live in the contaminated area near the derelict Chernobyl nuclear power station