LONDON (AA) – Workers at Britain’s Royal Mail on Tuesday announced two 48-hour strikes around Black Friday and Cyber Monday in an ongoing dispute over pay and conditions, according to the Communication Workers Union (CWU).

Black Friday takes place on Nov. 25 and Cyber Monday on Nov. 28. They are both huge consumer shopping events.

On Monday, Royal Mail made a pay offer, but the CWU called it a “surrender document” because it included changes to terms and conditions as well as redundancies.

The CWU will put the offer to its members for a vote but will recommend they reject it. The union will also put to its members a vote of no confidence in Royal Mail chief executive Simon Thompson.

Over 115,000 workers are involved in the escalating dispute.

“The CWU have announced four days of strike action which will damage our business further at our busiest time of year,” a spokesman for Royal Mail said Monday.

“The CWU is playing a dangerous game with its members’ jobs and the future of Royal Mail. We urge the CWU to withdraw these strikes for the good of our customers and our people.”

CWU General Secretary Dave Ward had said that “the current direction of Royal Mail does not benefit the company, the community or the country.”

“We still need to secure a decent future for this industry, and no attempts to attack our union and our members will change our determination in fighting for that. The current focus of the coming days will be negotiations that can hopefully achieve a sensible deal to end this dispute.”

Ward added that unless the dispute is resolved, industrial action would continue in the runup to Christmas.