The ballot papers will be sent to 125,000 Royal Mail workers in what will be the first national strike ballot since 2009. The ballot excludes Post Office workers.

The union disputes the settlement of its 2013 pay claim and changes to workers pension and is calling for clarity on the future strategy of Royal Mail. If a yes vote is reached, the union will give seven days' notice for strike action with the first strike date available from 10 October.

CWU deputy general secretary Dave Ward said: "We are dealing with a company that is preparing for privatisation with relish. While the union continues to fight privatisation we are also dealing with the potential realities for workers if there is a change of ownership.
 
"We are looking to reach a groundbreaking agreement on terms and conditions that sets unprecedented legally binding protection for workers in the event of a sale, and regardless of who owns the company.
 
"Postal workers know franchising, break up and sale of mail centres, distribution hubs and Parcelforce, along with the introduction of a new workforce on lower terms and conditions, are real threats in a race to the bottom with mail competitors for any new company.
 
"We want Royal Mail and the government to put protections in place that are both meaningful and lasting" he added.

Last month at the CWU policy forum, 500 representatives voted unanimously for a strike ballot of Royal Mail workers. It followed a consultative ballot in June in which 92% of respondents supported a boycott of DSA providers' mail and 96% were opposed to Royal Mail privatisation.