The Unison workers, who deliver samples, medication, linen and food, are claiming higher pay following the conclusion of a job evaluation report by the trust.

Unison North West regional organiser Paddy Cleary said: ‘It's extremely disappointing the trust has failed to act on the findings of its own report, which concluded drivers should be paid more for the vital work they do.

‘There's clear evidence the evaluation process wasn't followed. But instead of putting this right immediately, the trust has chosen to delay matters yet again by seeking additional advice that isn't needed.

‘Staff are left with no choice but to take further strike action. The trust still has time to do the right thing, implement the report findings and quickly ensure workers receive the higher wages they're due.'

A picket line will be in place from 7.30am at Prestwich Hospital, Manchester from Tuesday 21 April to Monday 11 May.

Marc Reed, director of capital, estates and facilities at Greater Manchester Mental Health NHS Foundation Trust (GMMH), said: ‘We have been notified by members of Unison who work as driver porters within our transport team that there will be planned industrial action taking place from Tuesday 21 April to Monday 11 May.

‘Robust plans are in place to minimise any disruption to deliveries to and from services, and the industrial action will only involve driver porters within GMMH's central transport team, based at the Prestwich Site. All other services will operate as normal and actions have been taken to prioritise the continuation of services throughout the industrial action period.

‘We remain in active discussions with Unison and local portering representatives and continue to work constructively to resolve the dispute.'