Royal Mail has warned that planned strikes by more than 100,000 workers will make the company “materially loss-making” in the current financial year.

Members of the Communication Workers Union (CWU) are set to walk out on August 26 and 31 and on September 8 and 9 in a dispute over pay.

In a statement to the stock market on Wednesday, Royal Mail said the decision to strike is an “abdication of responsibility” for the long-term job security of CWU members.

“In more than three months of talks, CWU has failed to engage meaningfully on the business changes required,” it said.

“The negative commercial impact of any strike action will only make pay rises less affordable and could put jobs at risk.

“The CWU has a responsibility to recognise the reality of the situation Royal Mail faces as a business, and to engage urgently on the changes required.

“Royal Mail remains ready to talk with the CWU to try and avert damaging industrial action and prevent significant inconvenience for customers. But any talks must be about both change and pay.

“Royal Mail has contingency plans in place and will be working hard to minimise disruption and restore normal service as soon as possible.”

Royal Mail said that, following the conclusion of negotiations with the CWU, it has given an unconditional 2% pay increase, backdated to April 1 2022.

A further 3.5% increase is available, subject to agreeing on a series of changes, the company said.

“The CWU rejected this offer, worth up to 5.5%, which would add around £230 million to Royal Mail annual people costs at a time when the business is already loss-making.

“In the Q1 trading update published on 20 July, Royal Mail announced it was losing £1 million a day and the proposed pay deal adds more than £0.5 million a day to that figure. This can only be paid for with meaningful business change.”

The statement added: “If the announced strike action takes place, it is expected that Royal Mail in the UK would be materially loss-making in FY2022-23.”

The CWU said the 2% rise had been imposed without agreement and the extra money on offer is based on changes to terms and conditions or meeting targets.

The union added that the pay increase was well below the soaring rate of inflation.