NHS Employers, an organisation representing NHS staff, said low morale among the workforce nationally is not surprising given several months of industrial action.
Health think tank The King's Fund said the latest findings from the NHS Staff Survey for England show workers are at "breaking point", and called on Prime Minister Rishi Sunak to look after staff as he attempts to bring down waiting lists.
Morale among staff at Southern Health NHS Foundation Trust was scored at 6 out of 10 in autumn 2022 – though this was up from 5.9 the year before.
Across the country, the overall morale score – which is a composite score of 13 questions, focusing on stress, work pressure and desires to leave – fell to its lowest point in the five years.
Morale was scored at 5.7 out of 10, down from 5.8 last year and a peak of 6.1 in 2020.
Danny Mortimer, chief executive of NHS Employers, said: "It is no surprise given that we have now witnessed several months of industrial action by NHS staff that those same staff, who have worked through extraordinary challenges over the past few years, have expressed their feelings of deep frustration in these responses.
"It is of course concerning to see that 17% of staff considering leaving for another job will do so as soon as they find one and that, despite the continuing efforts of health leaders to recruit and retain employees, the numbers of those willing to recommend the NHS as an employer has also dropped."
Mr Mortimer highlighted staff dissatisfaction regarding pay, while recent industrial action has been taken by nurses, doctors and ambulance workers, with staff seeking pay increases during the cost-of-living crisis.
The survey shows just 25.6% of staff across the country were satisfied with their current level of pay – the lowest level in five years and substantially down on a peak of 38% in 2019.
In Southern Health, 27.4% of staff were happy with their current salaries last year – down from 34.4% the year before.
Mr Mortimer called for the Government's NHS Workforce Plan – which aims to address concerns regarding the recruitment and retention and staff – to be published.
Sally Warren, director of policy at The King’s Fund, said the findings show "staff are being stretched to breaking point".
Ms Warren said: "Staff feel undervalued, under huge pressure and are questioning their roles in the NHS."
She added: "Looking after staff in the NHS should be the Prime Minister’s first priority if he wants to reduce waiting lists and waiting times."
Health and Social Care Secretary Steve Barclay said: "I am hugely grateful to all NHS staff for their hard work. Through the NHS People Plan, we’re taking action to make the NHS a great place to work, from investing in learning and development to better supporting staff mental health and wellbeing.
"We’re also making progress to recruit more staff, with more than 4,900 doctors and almost 11,100 more nurses compared to a year ago, and we will soon publish a long-term workforce plan setting out plans to support and grow the workforce."