Trade union Unite believes this decision could be the first step in closing the pension scheme altogether.
If Corus does not back down on its decision, the trade unions including GMB, Unite and Community will ballot their members on strike action, giving more information on this over the next few weeks.
The National Trade Union Steel Co-ordinating Committee issued the following statement: " [Members are] unanimous in their opposition to the move by Corus to close the pension scheme to new entrants. Representatives and shop stewards will be taking this powerful message of protest back to their workplaces.
"We want to make it very clear that the unions are united in their determination to tell our members the truth behind Corus' decision and to expose their motivation which is to close the pension scheme completely.
"Members have seen thousands of job losses across Corus, their bonus has been removed and now the company is attacking their pensions. Corus should be fully aware that the unions are saying enough is enough.
"Representatives have called for ballots for industrial action right across the company, so ultimately our members will decide."
The steel firm's announcement comes after its decision to shed more than 4,500 jobs at its UK plants.
Corus did not offer an official comment.
