THE threat of industrial action by steelworkers over the mothballing of a huge plant grew tonight as the Government pledged to do everything it could to prevent the steelworks closing down permanently.

Corus confirmed it would start mothballing the Teesside Cast Products site in Redcar tomorrow with the loss of up to 1,600 jobs, blaming an international consortium for pulling out of a contract halfway through a 10-year deal.

Union leaders attacked the decision to mothball the plant and stepped up warnings of industrial action to try to save the jobs, while workers said there was ''no chance'' it could be saved.

The Community union confirmed moves to ballot its members, while the GMB union announced it was also considering industrial action.

A ''credible'' consortium was said to be considering an 11th-hour bid for Redcar, and there were suggestions that at least two companies were interested in a possible sale.

But workers leaving the site tonight spoke gloomily about the prospects for a reprieve. Alan Blackwood, 57, who has worked at Redcar for 42 years, said he was now facing voluntary retirement, adding: ''I am just gobsmacked. It just feels to me that Corus doesn't want Teesside to exist.

''We are dead, gone, finished. There is absolutely no way it can be saved. I think I am more concerned about the company than the Government is.''

Linda Robinson, 50, whose family have been working at the steelworks for three generations, said her brother finished his last shift this morning and would never be going back.

She accused Business Secretary Lord Mandelson and Prime Minister Gordon Brown of talking ''platitudes'', adding: ''They say mothballing, but really it's closure. It is catastrophic for the community. The future is bleak.''

Lord Mandelson visited the region today and pledged: ''Politically, we are not going to walk away from this plant. We stand full square behind it. We will do everything we can to bring it out of mothballing and back into production as everyone around here wants to see.

''The reason it is not yet a tragedy is because it is not yet a closure of this plant. This plant will be maintained, its ability to reopen and resume operation will be protected by the company, and I have that assurance from them.''

Gordon Brown, speaking in Durham, said the Government was ''desperately looking'' for new investment, adding: ''I understand the frustration that people feel. There are wonderful workers at Corus. This is a good company, this is not a company that should be going under, but we have a problem.''

He blamed falling global demand for steel, decreasing prices, and in particular the international consortium which pulled out of the 10-year deal to buy the Redcar plant's output.

''We are trying desperately to find new investors for the future. We are talking to a number of investors about the future of Corus.''

Despite the Prime Minister's comments, Corus issued a statement confirming it will start to partially mothball the steelworks tomorrow.

''This is the direct result of the decision in April 2009 by a consortium of four customers responsible for almost 80% of the plant's business to renege on a binding 10-year contract.

''Since then, Corus has worked tirelessly to find an alternative long-term solution for Teesside Cast Products (TCP).

''By keeping the plant open, much of the time solely on internal orders, Corus lost approximately £150 million. The company therefore had no choice, in the absence of a strategic partner, but to announce the partial mothballing of TCP in December.

''The timing of the start of this process is determined by the availability of stocks of iron ore on the ground in Teesside. These have now run out.

''There has been speculation about potential last-minute bidders for the plant. Corus's position remains unchanged. This is a mothballing, not a permanent closure. TCP will be kept ready for a restart. Corus remains open to credible offers for TCP.

''Corus shares the concern of trade unions and Government about the implications of the mothballing for its employees and the Teesside area. The company has done everything in its power to avoid this outcome ever since the consortium first asked for TCP to be mothballed in November 2008.

''TCP has been at the top of the company's agenda throughout this period and Corus has at all times kept the highest levels of Government fully informed about TCP's situation.''

Keith Hazlewood, of the GMB, said: ''I have written to our general secretary seeking permission to ballot our members in the steel industry. Corus and the Government need to be more pro-active in examining the possible deals on the table to keep this plant open.

''We need an urgent meeting with the Prime Minister and for him to step in and take charge.''

Unite's national officer Terry Pye said the mothballing of the plant was a ''disgraceful charade''.

He said: ''The union has reason to suspect that Corus never had any intention of selling this plant and they now intend to close the site, which will have a devastating effect on the local community, which has a rich 150-year heritage of iron and steelmaking, ''Corus is trying to give the impression that it wants to mothball the Teesside site with a view to selling it once they have interested buyers.

''However, Unite think this is a smokescreen. We are aware that serious offers have been made to Corus that would allow production to remain at the plant, but the management has dismissed them all out of hand.''

Michael Leahy, leader of the Community trade union, said: ''Tata Corus have a moral and social responsibility to the workforce and to Teesside. However, by continually stonewalling potential buyers, Tata Corus are signing the death warrant for a more than 100-year tradition of steelmaking on Teesside.''