The planned strikes would be spread across October and November, said the Communication Workers Union (CWU), which represents 115,000 postal workers at Royal Mail. The union had already set out plans for strikes from late September to early October, Reuters reported.
The strikes come days after Royal Mail said it had informed the CWU that it wanted to "modernize the ways of working with them". On Tuesday, the company declined to elaborate on what changes they were specifically seeking, but said it was discussing it with the CWU.
"This is a significant announcement, but it is one which matches the level of anger our members feel at the way Royal Mail Group has treated them," CWU General Secretary Dave Ward said, referring to the strikes.
The union said the announcement follows the decision by Royal Mail Group management "to withdraw from major national agreements, push ahead with vicious cuts to workers terms and conditions and completely sideline the union."
In response, the company, which says it is losing 1 million pounds a day, called the announcement as the union choosing "the path of prolonging disruption over resolution".
The next strike action is scheduled for Wednesday September 28, according the CWU website.