Gary Rumble says he lost his job after his bosses at government-linked legal giant HWL Ebsworth spent several years trying to stop him advocating on behalf of abuse victims, fearing their outspoken employee might hurt their lucrative relationships with government departments.

He says the final straw was an article he wrote for Fairfax in December 2016, highlighting the plight of veterans who had suffered appalling and degrading physical and sexual abuse and branding their continued mistreatment at the hands of the Commonwealth a "disgrace".

Dr Rumble's unfair dismissal action, filed in the Federal Court in Canberra by his lawyers Maurice Blackburn, invokes the ACT law against discrimination on the grounds of political opinion.

But Ebsworth denies their former employee's claim, saying Dr Rumble was sacked because there was not enough work for him.

The firm also says the dismissal took place when he was at home in NSW, where it is not illegal to discriminate against a worker on the basis of political beliefs.

The firm intends to fight the case and has filed a detailed defence with the court.

But Dr Rumble's lawyers Maurice Blackburn are adamant their client is on firm legal ground.

"The law is very clear that employees in the Australian Capital Territory are protected from being sacked for expressing their political opinion," senior associate Alana Heffernan said.

Dr Rumble says he had no particular interest in the issue of abuse in the Australian Defence Force before 2011 when he took on the job, under the Gillard government, of leading the review of the government's response to decades of abuse in the nation's armed forces.

But the horrors he and his colleagues uncovered turned him into a passionate advocate for men and women who Dr Rumble says have endured decades of mental torment caused by the abuse they suffered.

He told Fairfax that he was determined not to turn his back on men who had suffered degrading sexual, physical and psychological abuse when they were boys as young as 13 in the Army, Navy and Air Force from the 1940s until at least the 1980s.

In the years since the major review was published, he has written to ministers, spoken repeatedly in the media and testified to Parliamentary committees in his quest for better treatment of victims, despite his legal bosses' repeated attempts to shut him up.

Documents filed to the Federal Court allege that Ebsworths believed Dr Rumble's strident advocacy risked offending ministers as well as senior figures at their clients, the departments of Defence and of Veterans' Affairs, potentially jeopardising tens of millions of dollars in taxpayer-funded legal fees.

Mr Rumble said he spent months of "uncertainty and isolation" in late 2016 and early 2017, waiting to see if his bosses at Ebsworth would carry out their threat to sack him, before he received a curt email on February 20, telling him he was fired but providing no reason.

Dr Rumble said the manner of the sacking, which came three days after he was recognised as Canberra's "Public Law Lawyer of the Year", was a humiliating experience.

"The manner in which it was done, on Sunday evening with a short email, terminating me immediately and requiring me to surrender all property of the firm immediately as if I was some sort of wrongdoer, was fairly humiliating, disrespectful treatment," Dr Rumble told Fairfax.

But he remains unrepentant about about his advocacy for victims.

"I'm having enough trouble sleeping having done it, but I'd be having a lot more trouble sleeping if I hadn't done it," he said.

HWL Ebsworth declined to comment.