The Western Trust’s dependency of more expensive agency nurses has almost doubled over the past three years.
Between 2012 and 2015 the local health authority spent a total of £6.6m on agency staff.
But expenditure has risen steadily.
The Trust spent £1.6m in 2012/13. This rose to £2.2m in 2013/14.
And last year it had risen to £2.8m.
The outgoing Health Minister Simon Hamilton revealed the information in response to an Assembly Question before he stepped aside from his post following the Stormont crisis.