GMB says porters, domestics, catering and security staff are angry because they get ‘worse terms and conditions than colleagues working at the same hospital'.

The workers have been outsourced to AGH Solutions (AGHS), a wholly owned subsidiary of Airedale NHS Foundation Trust.

The union claims AGHS uses its subsidiary status to not honour the NHS Agenda for Change terms and conditions, including NHS pensions, sick pay rates, annual leave and Sunday working enhancements.

GMB is calling for parity for everyone working across the trust.

Joe Wheatley, GMB organiser, said: ‘These workers are essential to the smooth running of the Airedale Hospital. Without them patients would not be safe or seen. It cannot be right that they are being treated as second-class workers.

‘The last thing our members want to do is strike and disrupt patients lives, but we've been left with no choice. It's time Airedale and AGHS recognise the skills of these vital staff and get back to serious pay negotiations.'

In response, Dennis Kentrop, managing director of AGH Solutions, said: ‘As an employer, we believe that we offer very competitive terms and conditions which attract talented individuals to the company and provide valuable opportunities for employment and development.

‘We remain committed to continually improving AGH Solutions Limited as a place to work and, following recent negotiations with GMB, we further improved upon our proposal.

‘I hope that we can continue to work in partnership with GMB to reach a resolution so our teams can carry on with the valuable work they are doing and focus on keeping our patients at the heart of everything we do.'

The strike ballot closes on 13 August, with any industrial action expected to begin in September.