An investigation by The Telegraph said whistleblowers had been targeted after raising concerns about over 170 patient deaths and 700 cases of poor care.

The report cited the case of nurse Michelle Russell who had spent eight years raising concerns about a staff member who had been allegedly harassing patients' mothers.

Russell said her life had been ruined and had been ‘pulled to pieces' during a Nursing & Midwifery Council hearing after being vindicated by in an independent investigation.

An NHS spokesperson said: ‘It is completely unacceptable for any member of staff to feel silenced or unable to speak up about issues affecting them or patients – not only should everyone working in the NHS feel they can raise concerns but they must know that they will be acted on and that they will be treated fairly – this is vital for ensuring that the NHS learns from mistakes and provides the best possible care for patients.'

The spokesperson said every NHS trust should be adopting the national Freedom to Speak Up policy, adding NHS England had recently asked all local areas to ensure staff have easy access to information on how they can raise concerns, including having a dedicated Freedom to Speak Up Guardian in place.

‘Where people are disadvantaged as a result of speaking up, NHS England has ensured there is additional help available with a national scheme in place so staff can receive additional intensive support in these circumstances,' the spokesperson said.

Regarding the case of Michelle Russell who was employed by the NELFT NHS Foundation Trust, NHS England said it had worked with Russell and the NELFT to ensure an independent investigation took place.

NHS England said it had offered Russell significant personal support over many years, including supporting her secondment.

NHS England said that while it ensured an independent review was commissioned, the NMC was solely responsible for its processes and findings.

Andrea Sutcliffe, chief executive and registrar for the NMC, said: ‘There's no place for sexual misconduct in society, and we took the concerns Ms Russell raised with us very seriously. We considered the evidence carefully and decided there was a case to answer, and we made that case at a hearing. However, an independent panel decided that the charges we brought in relation to Ms Russell were not proved. Understandably that has been very distressing for Ms Russell.

‘The Professional Standards Authority (PSA) reviews all hearing outcomes, and in this case found no fundamental issues with the hearing, our case presentation or the panel's decision. We respect the PSA's decision, and the registrant is currently subject to a five-year caution order after the panel found some separate charges proved.'