The Commonwealth's 160,000 public servants are to be stripped of some of their generous workers' compensation benefits as the government moves to end the "rorting and malingering" that has dogged the bureaucracy for years.

The government says the Comcare scheme is seen by the community as a "soft touch", "that invites rorting".

There will be a crackdown on mental injury claims, taxpayer-funded alternative therapies, public servants spending years or even decades away from their jobs and compensation paid over the "reasonable actions" of departmental bosses.

Under the Safety, Rehabilitation and Compensation Amendment Bill 2015 workers seeking a payout will have to prove their injury is work-related, in a change designed to prevent any repeat of the infamous "sex-in-a-motel" legal saga that cost taxpayers $600,000.

But lawyers are furious with one of the profession's peak groups, the Australian Lawyers Alliance, describing the proposed changes as harsh, unfair and an attack on the rights of injured workers.

Reform of the scheme has been on the cards since 2012 when a review urged sweeping reform to try to contain the cost of Comcare which at the time was running at a half-a-billion dollar loss.

Comcare has clawed its way back into the black, largely through a sharp rise in insurance premiums charged to government agencies, to $411 million in 2014, causing bitter resentment at the top of the cash-strapped public service.

One big premium payer, the ACT Government, lost patience with the pace of reform and announced in February it was taking its 20,000 employees out of Comcare after being slapped with a $95 million bill in 2014-2015.

Launching his legislation on Wednesday, Employment Minister Eric Abetz said Comcare was a "good scheme" but claims like the motel sex case had been undermining the system and ruining things for the vast majority of public servants who did the right thing.

"There are too many cases like this," he said.

"They simply encourage rorting and malingering, waste taxpayers' money and undermine the thousands of hard-working public servants who do not try to take advantage of the loopholes in the system."

If the government can get its bill through the Parliament, future claimants will face tougher requirements to take part in rehab programs and "injury management" as well as rules that any therapies will have to be "evidence-based" if taxpayers are to foot the bill.

Compo-funded expatriate lifestyles will be curtailed with payments cut off if the claimant is absent from Australia for more than six weeks.

There will be higher lump sum payments for employees with severe or multiple injuries, and lower payments for those with minor injuries, taking into account pre-existing conditions, according to a fact sheet distributed with the legislative changes.

There will be caps on medical and legal costs and taxpayer-funded carers will have to be qualified. The legislation will also introduce a "three-stage sanctions regime" enabling a claimant to be kicked off benefits if they refuse to comply with the insurer's directions.

But ALA National President Andrew Stone blasted the changes on Wednesday, saying Senator Abetz was using isolated example of extreme cases to justify an attack on the care and rehab of injured workers.

"The reality is that the changes proposed will make it more difficult for employees to get the care and rehabilitation they need, compounded by injured workers also facing greater pressure to re-enter the workforce prematurely," Mr Stone said.

"This includes through proposed harsher rehabilitation requirements, a reduction in the current weekly wage-loss payments, and the introduction of a harsher test workers will have to go through in proving work was a significant contributing factor to their injury."