Last year, Unison campaigning persuaded senior managers at the trust to move the support staff onto a higher salary scale, in recognition of the more complex jobs they now do.

Previously, the healthcare assistants had been on the lowest NHS wage band. However, the union successfully argued that the workers had been carrying out tasks – such as taking blood, performing electrocardiogram tests and inserting cannulas – that should have been paid at a higher hourly rate.

However, the union says the trust is refusing to compensate its employees properly for the extra work they undertook on the wrong pay grade. It says other trusts have resolved disputes with back pay offers that fairly compensate workers for additional duties and staff in Northumbria shouldn't have to settle for less.

Unison Northern regional secretary, Clare Williams, said: ‘None of the healthcare assistants want to go on strike. But the inability of senior managers at Northumbria to make them a serious offer has left them with little other option.

‘For years, staff worked way above their pay grade. It's only right that having moved them up the NHS salary scale, their managers give them a sensible amount of compensation to cover all the wages they were denied.

‘Elsewhere in the north east, healthcare assistants in Teesside, Sunderland and South Tyneside have secured far better back pay deals. There's no reason why staff in Northumberland should have to settle for less.

'The trust must do the right thing, get back into negotiations and come up with a significantly improved offer.'

In response, a spokesperson from Northumbria Healthcare NHS Foundation Trust, said: ‘Northumbria Healthcare NHS Foundation Trust worked in partnership with our local Staff Side last year and reached an agreement in principle to re-band the role of nursing assistant from Band 2 to Band 3 with effect from 1 April 2024, with pay backdated to 1 April 2022. We acted quickly to make the banding changes and pay backpay to those who were entitled to it.

 ‘As always, we are committed to working in partnership with our staff side colleagues on local matters, and we will do what is required to ensure the safe care of our patients.'

The 48-hour walkout by the staff begins on Wednesday 16 July.