Royal Mail managers that are members of trade union Unite are taking part in a ballot to vote on industrial action over pay.
Unite members will vote on whether industrial action should be taken, and whether or not that should include strike action.
The ballot will close on 21 April. If industrial action proceeds, it could involve approximately 4,900 Royal Mail managers.
The pay dispute relates to a 1.3% pay increase offer for the pay period beginning September 2015. This was rejected by 95% of union members.
Brian Scott, Unite officer for Royal Mail members, said: “The [organisation’s] final pay offer has already been rejected by 95% of Unite members, but the management remains unwilling to sit down and find a way through this difficulty.
“The dispute is about the 1.3% pay offer for some employees, with a non-consolidated lump sum for others. There has been no increase in overtime or allowances.”
A Royal Mail spokesperson added: “It is disappointing that Unite has chosen to ballot its members. However, a ballot for industrial action does not mean that any action will take place.
“Royal Mail has engaged Unite in serious discussion around its pay claim from September 2015. We maintain that we have put forward a fair and competitive offer, which recognises the efforts of our managers and compares well with current inflation levels.
“We want to reach agreement so that our managers receive their pay award as quickly as possible.”