Reports estimate that the industrial action could end up costing Royal Mail up to £260 million as businesses switch to other services to deliver their mail, the BBC reported.

The British Chambers of Commerce (BCC) said it was time for both sides to reach an agreement.

A spokeswoman said:

"The reputation of Royal Mail is being battered, and businesses are going without vital post whilst looking for alternative ways to get their mail delivered in the future.

"This dispute needs to be resolved and normal service resumed as quickly as possible."