British Steel has announced it is to cut 400 jobs from its worldwide operations.
The company, which employs 5,000 people, said the job losses were part of a "streamlining" process.
Most of the redundancies will be in managerial, professional and administrative roles across its businesses in the UK, Ireland, France and the Netherlands.
The Community trade union described the news as "a body-blow to the workforce".
Roland Junck, British Steel's executive chairman, said he was "sad" to be making the announcement.
"However, it's vital our transformation continues so we can build a sustainable future for the whole business, nearly 5,000 employees and many more people in the supply chain," he said.
"We're confident these proposals will help achieve this."
In a statement, the Community union said it recognised the "challenging times for UK steelmakers" and called for government support for the steel industry.
"This announcement will come as a body-blow to the workforce who have already made huge sacrifices to make the business sustainable," the union said.
"It is particularly disappointing the company has chosen to cut jobs so soon after celebrating a second successful year and first quarter profits of £21m."
British Steel was formed in June 2016 after Greybull Capital bought assets from Tata Steel.
The company employs 4,000 people at its Scunthorpe plant and has sites in Teesside, Cumbria and North Yorkshire.
It has not yet been confirmed which locations will lose staff.