Unison says a meeting with hospital managers earlier this week was ‘unproductive', so workers are stepping up the strike with five days of walkouts.

The union says theatre assistants are on the lowest grade in the NHS, but they carry out crucial clinical work, which should be paid at a higher level.

The employees, who work at three sites run by Leeds Teaching Hospitals NHS Trust, walked out for 48 hours in December as part of their campaign.

Unison says the employees should be moved to the correct pay grade and compensated for the extra duties they have already completed. The trust's refusal to pay staff fairly is out of line with other hospital trusts across the region, and around the country, says the union.

Leonie Sharp, Unison Yorkshire and Humberside regional manager, said: 'There would be no need for staff to be back out on the picket line if senior managers at the trust took this seriously.

‘Staff feel they have no option but to strike to make trust bosses realise how serious this issue is.

‘They carry out crucial tasks to make sure vulnerable patients are operated on safely. They just want to be paid fairly for the work they do.'

In response, Dr Magnus Harrison, chief medical officer at Leeds Teaching Hospitals NHS Trust, said: ‘We want all our colleagues to feel valued and able to raise their concerns. We are continuing to work closely with theatre colleagues and staff-side representatives to reach a resolution as soon as possible.

‘In the meantime, we have put plans in place to minimise disruption to patients during the periods of strike action.'