The union said the newspaper groups decision was even more surprising given the Mirror Group pension fund theft when under the control of Robert Maxwell.

But a spokesman for Trinity Mirror said: It is a way of controlling costs way into the future - we are talking well over the horizon. All existing plans are performing well and are not affected.

The union will consult with its members and raise the issue with MPs, government ministers and the TUC, according to national officer Chris Harding.

Existing Trinity Mirror staff have until 28 February to join the schemes.

New employees will be offered a new plan, to which the companys contributions and costs are estimated to be 12% of each employees salary.

We believe that the new scheme is fair and equitable. It show the companys commitment to providing for its employees, said the spokesman.