The union representing 12,000 Royal Mail managers has threatened to ballot its members on strike action if the state-owned postal operator goes ahead with plans to close its pension scheme for all staff.

Emerging from talks with management on Monday afternoon, Unite said Royal Mail was preparing to start consultations with staff over plans to wind up the final-salary pension scheme.

Under the plans, members of the final-salary scheme would be offered a pension linked to their average pay. This would hit managers particularly hard, since they earn their highest pay in the years before they retire.

Pensions accrued under the closed final-pay scheme would be treated like a deferred pension, increased in line with inflation or 5 per cent if higher. If they remained in an open final-salary scheme, they would keep pace with earnings. New employees could join a money purchase scheme.

Royal Mail refused to comment on the union’s statement, and said it had yet to finalise its proposals. There would be “genuine consultation” on those proposals. Its commitment was to continue to provide a “defined benefit” pension for existing members.

Adam Crozier, chief executive, had said in February that the group wanted to safeguard the final-salary pension scheme for existing members.

One complication is that an average pay pension scheme may be more attractive to most postal workers, who often earn more when they are younger through overtime. A person close to Royal Mail said the proposals would reflect the input of all the stakeholders in six months of talks.

Royal Mail faces strikes by members of the largest union over pay and modernisation. The CWU announced two 48-hour walk-outs last week after the breakdown of talks in the summer.