The majority of workers at Norfolk and Suffolk NHS Foundation Trust (NSFT) claim staffing levels since the redesign do not provide a safe service, according to a survey.

The findings, from a survey of Unison members, claim the impact of service change is leading to poor outcomes for those who rely on NSFT services and has had a “devastating impact” on staff morale.

NSFT was formed in January 2012 after Suffolk Mental Health Partnership NHS and Norfolk and Waveney Mental Health NHS Foundation Trust merged.

The results have left Unison to raise a formal grievance with NSFT, which provides mental health services across the two counties, on behalf of its members and have called on the service to call an immediate halt to its reorganisation.

A total of 81% reported staffing levels following the redesign do not provide a safe service, 86% say they are not providing a good quality service and 54% report feeling unsafe at work. While 56% have considered whistle-blowing and 42% have reported clinical concerns.

The union has grave safety concerns regarding the ongoing implementation of the service strategy with grievances over unsafe staffing levels, unmanageable workloads and a failure by management to act on concerns raised repeatedly by staff about the impact on quality and safety of services of the current service changes.

Emma Corlett, NSFT branch of Unison spokeswoman, said: “Our members have been raising escalating concerns over a number of months about the impact of the service reorganisation, which the NSFT board have consistently failed to address.

“Things are now at such a critical point, that immediate action needs to be taken to address current risks to the safety and quality of patient care.

“Why is that everyone can see the crisis we are in, apart from the people who are paid to take responsibility?”

Andrew Hopkins, acting chief executive of NSFT, said the grievance letter from Unison “came as a surprise” as the trust has worked with the union over the past two years on the service strategy.

“We acknowledge that there are areas of improvement to be made but are disappointed that they have resorted to this approach, rather than engage in discussions with the management of the trust,” he added. “We reject any suggestion that the services we provide are unsafe. We have recently been subject to a review on the risks to quality of our services by KPMG on behalf of Monitor and the Care Quality Commission has completed inspections of a number of our inpatient and community services.

“While some concerns have been highlighted, which the trust is addressing, these reviews do not paint the picture that Unison is presenting.

“We will carefully consider the points that Unison has raised and will respond in due course.”