The pay gap between federal government departments is growing.

The gap between the lowest and highest paid public servants in the Executive Level 1 band is at nearly $53,000, up from around $47,000 four years ago.

The $52,647 difference is between the highest paid EL1 at the Australian Institute of Aboriginal and Torres Strait Islander Studies ($98,639) and the highest paid at the Australian Office of Financial Management ($151,286).

It means that workers considering moving to another agency could have their pay cut if they take more senior roles elsewhere.

Dr Samantha Johnson from the University of New South Wales' public service research group said a lack of mobility between departments is not helpful.

“That means you've got knowledge shared, you've got cultural change that can happen when people move around the place and bring different experiences into organisations,” Dr Johnson said.

“Which is one of the reasons why senior executives often have had a career that has greater breadth and less depth, because they've moved across different departments, they have different exposure to political realities, to cultures, to organisational ways of behaving, and they take that experience with them.

“[Salaries are] not the be all and end all, you can't be black and white about this.

“There are many people who will put the financial aspects aside and they will move to develop a career as they choose and their pay will go up a bit and down a bit, and they won't be too worried about it.

“But there are other people who will find it more difficult and be more reluctant to move if they believe that the financial loss is too great, then it can be an inhibitor.”