Hundreds of staff at the Royal Devon University Healthcare Trust were off sick during Christmas week, new figures show.
A health and social care think tank said the high number of NHS staff absent on Christmas week across England is "concerning", and warned soaring flu cases mean absences may not fall in coming weeks with the NHS under increasing pressure.
NHS England figures show an average of 668 staff members at Royal Devon University Healthcare NHS Foundation Trust were off ill each day between December 23 and 29.
This was up from 641 in the same period the year before.
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Further NHS Digital data shows 11,391 full-time equivalent staff were working at the trust in August, the latest month for which data is available.
It suggests around 6% of the workforce were absent during Christmas week.
Across the country, an average of 50,000 NHS staff per day were absent from work.
It was up from almost 47,000 the previous year, but down from about 60,000 in 2022 and nearly 72,000 in 2021 which were affected by the coronavirus pandemic.
These absences were due to sickness or self isolation with Covid-19.
Dr Billy Palmer, senior fellow at the Nuffield Trust, said the number of NHS staff absent from work on Christmas week is "concerning".
He added: "Staff absences can disrupt care for patients, increase costs and put additional pressure on those staff at work.
"Previous research has also established that staff who have been off sick are more likely to leave the NHS in the future."
Dr Palmer also warned soaring flu cases mean the number of absences is not guaranteed to fall in the next few weeks.
Across all NHS trusts that submitted data in the South West, an average of 4,596 staff members were absent each day during Christmas week.
Meanwhile, separate NHS Digital figures show anxiety, stress, depression and other psychiatric illnesses was the most reported reason for sickness in July, accounting for over 606,800 full time equivalent days lost and 26% of all sickness absence.
At Royal Devon University Healthcare NHS Foundation Trust, 4,820 FTE days were lost due to ill mental health in July, responsible for 25% of all absence.