The employee, based at the retail giant's London head office, contacted the media last week over proposals to reduce redundancy payouts by up to 25 per cent.

The firm confirmed it was consulting with staff representatives on its Business Involvement Group over the move, which would limit maximum payouts from 70 weeks to 52 weeks depending on length of service.

The man has been suspended from duty and will face a disciplinary hearing next Monday. The GMB union said it will represent the worker at the hearing.

A spokeswoman for M&S said: "This is an internal matter and we are not commenting any further."

The GMB said it feared the company was preparing to make job cuts because of the changes to redundancy pay, which it wants to introduce from next month.

General secretary Paul Kenny said: "We are fearful that job cuts are on the way at M&S. Why else would they cut their existing policy if they did not intend to use it?

"Why do people at the bottom get the sack on the cheap while the top bosses get large payouts even when they leave having messed up?"

M&S, which issued a shock profit warning in June, said it had not reviewed redundancy benefits since 2006, adding that its new terms would still be more generous than most competitors.

The move heightened fears over job cuts as the group feels the brunt of a consumer spending squeeze, although the company did not comment on possible redundancies.

According to a report last week in the Times, which has seen an internal memo outlining the proposed changes, a typical 49-year-old employee with 30 years of service would see their possible pay-off fall from £35,000 to £26,000.

Those aged over 41 would get three weeks pay per year worked instead of the current 3.75, while staff aged between 22 and 40 would receive two weeks instead of 2.5.

The GMB union contrasted the proposed changes with the £500,000 handed to Steven Esom, M&S's former director of food, who left in July.