A record number of staff left their posts at South West London and St George's Mental Health Trust last year, new figures show.
It comes as the number of resignations across England soared, with nursing, doctor and midwife trade unions highlighting poor pay and a lack of mental and physical support as critical reasons for the exodus.
NHS Digital figures, which are rounded to the nearest five, show around 395 NHS staff resigned from their roles at South West London and St George's Mental Health NHS Trust in 2021-22.
This was up from approximately 345 in 2019-20 – the year leading up to the coronavirus pandemic – and the highest number since records began a decade earlier.
Across the country, 140,000 staff members resigned last year – up from 99,000 the year before – while an average of 101,000 staff resigned annually in the nine years before the pandemic.
The figures cover medical and administration staff. A resignation does not necessarily mean the staff member has left the NHS altogether, as the figures also include any promotions and relocations.
Pat Cullen, general secretary and chief executive of the Royal College of Nursing, said: "Years of underinvestment – including a decade of real-terms pay cuts – means record numbers of staff are leaving the NHS.
"Staff are leaving, realising they can get similar or better pay in supermarkets and retail without the stress of the job, and poor pay is creating severe staff shortages and making patients unsafe.
"Nurses, patients, and the public deserve better than a government that won’t listen."
Among the departures across England last year were 30,740 nurses and health visitors who voluntarily left their posts – the highest number on record and a 13% increase on 2019-20.
Of them, 100 were based at South West London and St George's Mental Health Trust – in line with 2019-20.
Meanwhile, the number of hospital and community health service doctors across the country resigning also reached record levels during the pandemic, rising from 8,225 in 2019-20 to 9,305 last year.
Dr Latifa Patel, chair of the representative body and workforce lead at the British Medical Association, said the rise in resignations is unsurprising due to the difficulty in finding a "healthy work-life balance".
Dr Patel added: "Fixing the workforce crisis isn’t just about recruiting more people, but also about retaining the staff already in the NHS. This starts with the Government paying them fairly, and publishing its NHS workforce plan as soon as possible."
The Royal College of Midwifery also said falling pay is a primary issue for many who leave the profession.
An RCM spokesperson said: "Midwives have seen over a decade of pay stagnation, and feel undervalued and burnt out.
"Now is the time for the Government to act – to offer midwives a decent pay deal and start tackling the serious problems facing our maternity services."
A record 2,260 midwives voluntarily resigned across England in 2021-22
The Department for Health and Social Care said it has given 1 million NHS workers a pay rise of at least £1,400 this year, as well as a 3% cost-of-living pay increase last year.
A comprehensive workforce strategy to help recruit and retain more staff will be published this year, a spokesperson added.
They said: "There are already record numbers of staff working in the NHS, with 4,700 more doctors and over 10,500 more nurses compared to last year, and we are committed to 50,000 more nurses in the NHS by the end of this parliament."