The union that represents Royal Mail workers has reacted angrily to the company’s latest pay offer and programme for change, accusing it of a “declaration of war on posties” and raising the prospect of further postal strikes in the runup to Christmas. Royal Mail has proposed what it called a new “conditional pay-for-change offer” to the Communication Workers Union (CWU), in an attempt to end a long-running dispute over pay and conditions. The offer includes a 7% salary increase over two years, as well as a lump sum payment worth 2% of pay this year. The pay offer comprises a 5.5% increase for the current financial year, including 2% that has already been paid. In addition, workers would be paid an additional 1.5% from April 2023. Royal Mail said the offer was subject to the CWU agreeing to a programme of changes to working patterns at the 500-year-old firm, including alterations to Sunday shifts, different start times and more flexible working. The company, which employs about 140,000 people, has persistently argued that such changes are necessary to allow it to compete in the growing parcel delivery market. Royal Mail’s chief executive, Simon Thompson, said on Monday: “Royal Mail made a loss of £219m in the first half of the year. This once again demonstrates that the need for change at Royal Mail is urgent.” He urged CWU leaders to accept the offer and call off further strike action, adding: “We have always been clear that the more we can change the business, the more we will be able to pay our people – both now and in the future.” However, the CWU described these changes as “unacceptable” and called the pay offer “derisory” and “well below projected inflation for both years”. Royal Mail’s new offer came a day after the CWU called off a fresh series of planned strikes over the next two weeks, after a challenge by the company. The union said over the weekend that it had decided to withdraw industrial action notices up until 12 November, after a letter from Royal Mail’s legal team. The two sides had been holding talks at the conciliation service Acas on Monday before Royal Mail announced its increased pay offer and proposed changes to working practices. The CWU accuses the company of “imposing change rather than negotiating it” and vowed that postal workers would vote on further strike action. The improved pay offer is not applicable to CWU members at Royal Mail who work for Parcelforce, nor for fleet employees – those responsible for maintaining the company’s vans and lorries – who are in separate bargaining units. The CWU said the company was trying to bring in new workers on “lower terms” and accused it of “introducing owner-drivers into Royal Mail – a service that will be comparable to Uber.” A CWU spokesperson said: “These proposals are about dismantling a 500-year-old service and destroying the lives of those who serve it. Make no mistake – Royal Mail bosses have just declared war on your postie.” About 115,000 Royal Mail workers who are CWU members have previously taken strike action over several days since August. The strikes and a decline in parcel volumes have previously prompted Royal Mail to warn that it may need to cut up to 10,000 roles by next August. It cautioned earlier in October that it expected to make an annual operating loss of about £350m in the year to the end of March. On Monday, the UK government said it had cleared Royal Mail’s largest shareholder – Vesa Equity Investment, an investment vehicle controlled by the Czech billionaire Daniel Křetínský – to increase its stake above 25%, after a national security review into the company’s ownership. The Guardian understands that talks between Royal Mail and the CWU have not broken down, and the company is urging the union to put its latest pay offer to members. The CWU has criticised Thompson for failing to attend the talks at Acas on Monday, where the CWU’s general secretary, Dave Ward, was present. Royal Mail said Thomson was unable to attend because of other engagements, but would attend in future, adding that the company was represented at the negotiations by another board member.