Tata has announced that it will cut 1,200 jobs from its steel-making facilities in Scunthorpe and Scotland.
Around 900 redundancies will be made at the firm's Scunthorpe plant, with a further 270 at its Scottish Dalzell and Clydebridge sites and a small number at other locations.
Karl Koehler, chief executive of Tata Steel's European operations, said: "I realise how distressing this news will be for all those affected. We have looked at all other options before proposing these changes.
"We will work closely with affected employees and their trade union representatives. We will look to redeploy employees, wherever possible, and minimise employee hardship.
"The UK steel industry is struggling for survival in the face of extremely challenging market conditions.”
Tata said the job losses were in response to a shift in market conditions caused by a "flood" of cheap imports, particularly from China, a strong pound and high electricity prices.
At its height, in the 1950s, steel-making in Scunthorpe employed close to 30,000 people in the town. However, these numbers have slowly declined over the last 60 years.
Liz Redfern, leader of North Lincolnshire council, admitted it would be a challenge to replace the relatively high-paid and high-skilled jobs at the steelworks.
"This is a steel town. The workers are very proud workers, skilled people and it is a very sad time. One job loss is one job loss too much. And we want to be here ready to support them," she said.
Meanwhile, the Scottish Government has set up a task force chaired by business minister Fergus Ewing, which will meet next week to look at ways to keep the plants open and support those workers facing redundancy.
First Minister Nicola Sturgeon said: "My government is determined to fight for a future for our steel industry. We will leave no stone unturned in our efforts to keep the plants open and support the 270 staff affected by today's announcement."
In Westminster, business secretary Sajid Javid told MPs that more infrastructure contracts could be offered to UK steel manufacturers in a bid to support the flagging industry.
The escalation of the crisis comes as Chinese President Xi Jinping visits the UK for a formal visit. With the industry’s failure being partially blamed on cheap Chinese steel exports, David Cameron said he would raise the issue with the president.
Cameron told MPs at the House of Commons yesterday that the UK's relationship with China was "at such a high level that there is no subject off the table" and added that "of course" the steel industry would be discussed.
The announcement amounts to another blow to UK steel, following the recent closure of the steel plant at Redcar which resulted in 1,700 job losses.