NHS England workers took more than 625,000 sick days for mental health in the space of just one month, according to new Government data.
Anxiety, stress, depression and other psychiatric illnesses were the most given reasons for sickness absence days.
These accounted for nearly one third of all sick days across the health service in June this year.
Official data shows staff took 625,834 days off for mental health, a 13 per cent increase on the same month the previous year.
The new figures take the total number of mental health-related sick days up to 3.6 million in the first half of this year.
TRENDING
Stories
Videos
Your Say
When broken down by profession, "back office" staff like those in HR, finance, communications, legal and other admin roles took the highest percentage of sick days for mental health.
More than 40 per cent of the sick days taken by managers and senior managers among NHS infrastructure staff were put down to mental health.
The same reason was given for fewer than 15 per cent of the sick days taken by first-year doctors.
Across all NHS staff, mental health was cited as the reason for absence nearly 30 per cent of the time on average.
Senior managers cited mental health as the reason for their absence three times more than first-year doctors
|GB NEWS
The so-called mental health crisis among NHS staff appears to be getting worse.
When the health service first started recording the reasons for sickness absence in 2019, mental health days averaged around 400,000 a month.
A spokesman for the British Medical Association said: "These figures are dreadful, but sadly not surprising... This is the result of a workforce who have been struggling for years to look after patients in a health system that is under unrelenting, severe pressure.
"The impact of rising patient demand, chronic understaffing, and inflexible and unsupportive working arrangements is fuelling the worrying rise of mental-health related illness among doctors."
READ MORE ON THE NHS:
Mental health was the most given reason for sickness absence in the NHS in June
|GB NEWS
Elliot Keck of the Taxpayers' Alliance said: "Larger and larger sums are being poured into the health service, yet rising sickness rates mean fewer staff on the frontlines and more pressure on those left behind.
"The Government must get serious about tackling the mismanagement that is driving staff to burnout and clamping down on absenteeism related to mental health."
Last year, more than 500,000 British patients sought healthcare overseas to try to avoid lengthy waiting times.
According to the British Medical Association, the waiting list for treatment in England stood at 7,414,794 in August.
Of that number, nearly three million people had been waiting more than 18 weeks and nearly 200,000 patients had been waiting over a year for treatment.
An NHS spokesman said: "It is totally unacceptable that sickness absence rates are this high - particularly in non-patient-facing roles.
"The NHS is offering a range of mental health and wellbeing support to help staff stay well and feel supported at work, which should also help bring sickness absence down to more sustainable levels."
More From GB News