The union has accused the two firms' management of ditching the scheme to plug a hole in its pension fund by, the union claims, cutting its future contributions by up to 70%.

"This is disgraceful treatment of long-serving loyal workers who have stood by the company during some very difficult times. Those employees are calling on the management to think again and come up with a plan for to save their pensions," said Amicus national officer Ann Field.

A union delegation is meeting with the firms' management on Wednesday (14 March) to try to break the deadlock.

In January, WHSmith proposed closing its final salary pension schemes, a move that would affect 2,000 employees, or 11% of its total staff.