Dave Hulse, GMB national officer, also warned power costs had to be competitive for intensive users so that “the push for low carbon does not drive heavy industry out of the UK.”
He added: “The GMB will work with the company and others to mitigate the job losses and to avoid compulsory redundancies.
“GMB will want to assess how the UK is losing out due to the weakness of the euro sucking imports into the UK and the extent to which higher power costs here than for EU competitors is leading to job losses.”
Some 550 Tata Steel jobs in South Yorkshire are under threat - including 490 at its Thrybergh site in Rotherham.
The firm plans to end production of commodity grade bar in the face of “crippling electricity prices” and the cost of exports due to a strong pond.
Gareth Stace, director of UK Steel, said a package of compensation measures were announced in last year’s Budget, but steel firms were still paying 70 per cent of the planned reductions - which were not due until April next year.
He added: “It’s frustrating, when fully implemented it will bring us broadly in line with Germany.”
Unite regional officer Doug Patterson said: “Unite will be working hard with the other steel unions at Rotherham to ensure that there are no compulsory redundancies – and we will be pressing that message strongly at upcoming meetings with the Tata management.”
Rawmarsh Ward Councillor, Simon Evans: said: “The loss of so many jobs will be a big blow to school-leavers in Rawmarsh who hope to find work in their local area. The history of Rawmarsh and Parkgate is deeply intertwined with the history of steel production and I hope this tradition continues in our village long into the future.”
A spokeswoman for the Department of Energy and Climate Change said keeping energy costs down for business and consumers was a key priority for Government.
She added: “We are working closely with industry to reduce business energy costs and improve competitiveness.”
A Department for Business Industry and Skills spokesman said: “The Government has paid £35 million in compensation to steel companies to help offset electricity costs and is looking at what further help could be provided. As part of the transition to a low-carbon economy, we need to ensure that energy intensive industries remain competitive.
“We have taken steps to offer relief to those businesses most affected by the rising cost of electricity. These include relief for intensive users. We are on track to deliver additional reliefs later this year, subject to European Commission approval.”