The Frimley Health NHS Foundation Trust spent more than £38.6 million on agency and contract staff in the year 2015/16.
Figures exclusively obtained by Get Surrey show the figure was up almost £8.8 million from the previous year.
In 2015/16 the trust spent £38,686,000 on temporary workers, up 29% from the £29,897,000 figure in 2014/15.
The Frimley Health NHS Trust operates three main hospitals: the Frimley Park in Frimley ; Heatherwood in Ascot; and Wexham Park near Slough.
It also runs outpatient clinics and diagnostic services from Aldershot, Farnham , Fleet, Windsor, Maidenhead, Bracknell and Chalfont St Peter.
In total the trust serves around 900,000 people in Surrey, Hampshire, Berkshire and south Buckinghamshire.
The 2016 annual report from the trust admits it has to look at the spending on agency and contract staff.
In the “key issues and risks” section, it says: “While the trust is on course to reach financial stability, it faces a challenge to significantly reduce spending on agency staff to cover vacancies.
Read More at: GetSurrey (17th January 2017)