The federal workplace insurer is currently fighting more than 500 cases in the Administrative Appeals Tribunal, mostly against public servants unhappy about their compensations claims being knocked back.

Responding to criticism from lawyers on Wednesday that unfair decisions were causing a surge of appeals, Comcare was unapologetic for its "robust" approach to claims management that it conceded was driving a rising number of appeals.

The Canberra Times reported on Wednesday that disputes lodged in the Administrative Appeals Tribunal against compensation decisions by the insurer were rising year-on-year as part of a "surge" of public service workplace disputes flooding through review systems.

But a Comcare spokesman said it was also important to note the number of appeals that were dropped or thrown out before they even reached hearing stage.

"In the current financial year, for example, more than one third of appeals were withdrawn or dismissed," the spokesman said."Our decisions are standing up.

"Comcare has finalised 433 matters in the AAT to date in 2014-2015, with Comcare's decision affirmed in 71 per cent of matters that go to hearing."

It was also revealed on Wednesday that the Public Service Commission believed some public servants though Comcare was a "soft touch" for dodgy claims.

But the spokesman said the Comcare was taking a tougher approach to claims of workers' compo and the harder line was driving the number of claims.

"The jump in the number of appeals against our determinations was driven by more robust claims decisions by Comcare, and more claimants appearing at the Tribunal without legal representation," he said.

"Claimants who represent themselves have a greater propensity to appeal against our decisions, and there has been a steady increase in the number of these appeals over the past three financial years.

"The reasons behind a claimant lodging an appeal are not always immediately clear to Comcare."