A union representative says the Cairns Hospital emergency department (ED) in far north Queensland is struggling to cope with unprecedented patient numbers and the situation should be declared a "disaster".

The hospital has reached the highest 'escalation level' several times this week due to record-breaking ED presentations.

Dr Sandy Donald from the Together Union said the situation was unsustainable and managements response had been inadequate.

"There should be staff who can be called in and if there are none, they haven't got enough staff," Dr Sandy Donald said.

"Secondly, you can reduce activity that is not urgent that takes up staff and beds, and then if you either can't do that or that doesn't solve the problem, you call for help from outside.

"There are places they could put patients but either there is no disaster plan or there is no will to implement it, and either way, I have talked again and again to the staff in ED, they are working their hearts out but it's not sustainable.

"I've seen people who look absolutely exhausted and they're getting to the point where they're getting broken."

However, Cairns and Hinterland Hospital and Health Service CEO Julie Hartley-Jones said it had taken "every possible measure" to deal with the surge, including opening 25 extra beds and cancelling non-urgent elective surgery.

She said all incoming patients were triaged and those needing urgent attention would be treated appropriately, although others may need to wait longer.