Morrisons is planning to close its salary-linked pension schemes in a move that will affect around 8,000 workers at the grocer.
Letters consulting staff about the changes, which would save Morrisons as much as £10m a year, were sent out on Friday.
It comes just weeks after supermarket rival Tesco revealed it was closing its own defined-benefit scheme.
Morrisons closed its two defined-benefit pension schemes to new members more than five years ago, but the latest changes will prevent staff who are already on the scheme making any further contributions to them.
Any benefits already built up by members of the scheme will be unaffected, but employees will now have to move to Morrisons’ cash balance scheme for any future accural.
Newer staff have been on this scheme for the past three years.
Morrisons human resources director Emily Lawson said: “This proposal is intended to provide fairer pensions benefits to all colleagues, ensuring that those doing the same role primarily have access to the same benefits.
“These are only proposals at this stage. Before any final decisions are made we will be entering into a consultation process with affected colleagues and their representatives.”
But shopworkers union Usdaw said the change would be worrying for its members, adding that they were “in the process of agreeing a timetable for discussions” with Morrisons.