"There needs to be a step-change in the level of government involvement with Tata, its customers and the unions," GMB General Secretary of Community Roy Rickhuss said in a statement.
The jobs are expected to go mainly at Llanwern in Newport, where its mills will stop running. Tata Steel in a statement said it needs to "reduce costs and focus on manufacturing higher-value products".
Ending a major dispute at the UK arm of Tata Steel, all the four trade unions have accepted the proposals for changes to the British Steel Pension Scheme that will keep it open.
The decision puts on hold what could have been the biggest UK steel sector strike in 35 years.
According to Roy Rickhuss, General Secretary, Community Union, Tata Steel could still to avoid the strike situation but only if they are prepared for meaningful discussions.