The industrial action, which began in February, involves both pathology and clinical engineering staff based at Queen's Hospital in Romford.

Pathology staff are striking over plans to impose a new shift system and over the 'failure of the trust to tackle bullying, harassment, and discrimination within the department'.

In clinical engineering, staff strongly oppose the outsourcing of their department and the proposed transfer of roles to Siemens Healthineers. This would erode terms and conditions and would not benefit staff or patients, according to Unite.

Sharon Graham, Unite general secretary, said: 'Unite will not stand by while these workers suffer bullying and have their jobs, pay and working conditions attacked. They have their union's complete support. Strikes will not end until these issues are resolved by the trust.'

Following the initial strike action on 11, 12 and 13 February, the trust invited Unite to talks. Senior management then admitted they were unaware of the workers' other concerns despite them being 'well known and publicised'. They also restated that the pathology shift changes would be imposed and failed to put forward any further proposals towards resolving the dispute.

Unite said notes sent by management after the meeting 'mischaracterised' what was discussed.

As a result, a further five days of strike action has been scheduled from 9 March to 13 March. The strikes will cause disruption to blood tests and other laboratory services carried out by the pathology workers for the trust and GP services. The maintenance and management of medical technology carried out by the engineering workers will also be disrupted.

Unite regional officer, Sujata Virdee, said: 'The trust's continued appalling treatment of these workers has only strengthened their resolve. Unite's door remains open for genuine negotiations, and we expect the trust to come to the table with substantive proposals without further delay. Strikes will continue to escalate until that happens.'

In response, trust chief executive, Matthew Trainer, said: ‘We're disappointed Unite have called a second strike which will have an adverse impact on our patients. 

‘We need to make changes to the shifts our staff work in pathology because we are one of the few trusts that don't have a 24/7 service. We recognise the impact this will have on colleagues who will be affected by this change and we're willing to offer a level of pay protection that is higher than elsewhere in the NHS.

‘We're keen to continue negotiating and we need Unite to agree to provide safe cover.'