A ballot of Royal Mail workers on a deal struck last month to end a bitter dispute over pay, jobs and working conditions has been suspended as the row between the postal firm and its union threatened to reignite. The Communication Workers Union (CWU) said it had become clear the environment in which it was attempting to achieve the agreement remained “toxic”. The union said on Wednesday it would suspend the previous timetable for a member vote until it was satisfied that “attacks” on its members have ended. Royal Mail agreed a new deal with the union in April after months of tense negotiations. The postal service operator blamed the strikes for a £1bn loss reported last week, and its chief executive, Simon Thompson, resigned earlier this month. In a message to members, the CWU’s general secretary, Dave Ward, and its deputy general secretary, Andy Furey, claimed the company had not stopped “attacks” against union members in the workplace. They said the proposed agreement, set against the “most brutal dispute in our history, a self-inflicted but very real financial crisis for the company and jointly agreed need for change”, would secure the future of the company, jobs, and the service. However, they added: “What has become clear is the environment we are attempting to deliver this agreement in remains toxic. “Royal Mail Group has not stepped back from their attacks in the workplace. This became more evident when they announced their quality of service results and failed to take any responsibility whatsoever for the disastrous position the company finds itself in. “Unless Royal Mail Group openly accept that their culture of imposition and the ‘our business to run’ mantra must go – then the integrity of the negotiators agreement will be irreparably damaged.” The CWU said it still backed the deal but wanted Royal Mail to bring in immediate measures to “restore quality of service”. That would probably include steps to address missed delivery targets highlighted this month by Ofcom, the regulator. Some communities in the UK have become “postal deserts” – where first-class mail can take two weeks to arrive. The union said it had made it clear to Royal Mail that unless quality of service is restored and “failed revisions” affecting workers were tackled, the business will not succeed. The union’s postal executive said it had decided to suspend the vote on the proposed national agreement until moves were made to restore quality of service and “genuinely review all failed revisions”. The union also demanded a “mass zoom meeting” between the company and every CWU representative, and for the company to give every branch their proposed finishing times. Shares in Royal Mail’s parent company, International Distributions Services, dipped 2% on the CWU announcement, before recovering some ground. A spokesperson for Royal Mail said: “We fully support this deal and hope that CWU members accept it in the forthcoming ballot. The need to change is critical so that we can improve our quality of service, deliver for our customers and get back to profitability. “The sooner we can get a positive ballot result the sooner we can give our people the pay rise that we have agreed with the CWU and provide greater job security.”