The groups, dealing directly with ex-services personnel making claims for injuries acquired in service, have urged overhaul to the government's compensation program for veterans.

Away from national attention, trained earlier this week on Virgin Australia's plan to thank veterans on flights and give them priority boarding, the inquiries into compensation and rehabilitation for ex-military personnel have received hundreds of submissions.

Among 150 sent to the government's economic advisory body, the Productivity Commission, law firms have called for a compulsory time limit to stop prolonged waits for financially stressed veterans seeking compensation. Advocates for ex-services personnel want an end to problems in claims handling at the Department of Veterans' Affairs.

The department, using injections of federal money to improve the compensation program, said it had cut claim wait times and that technology upgrades were speeding up decisions.

Law firm Maurice Blackburn said many clients had reported waiting years for the department to process their claim.

Financial stress, worsened by the agency's delays, could cause or aggravate psychological injuries.

"Most of these veterans were medically discharged as a result of service-related injuries and were unable to work. They were unable to access benefits until DVA processed their claims. The financial difficulties caused by these delays resulted in some veterans almost losing their homes," the company said.

Veterans have long called for change to the government's compensation program, which is complicated by its underlying tangle of legislation. In response, the Coalition has begun upgrading technology at the Department of Veterans' Affairs in reforms that have earned cautious welcome from advocates.

The department has reported meeting its targets in deciding on claims, and delivering income support, allowances, and other compensation last year. Wait times dropped as it cut the number of systems needed to process 85 per cent of claims, its 2017-18 annual report said.

The Veterans' Affairs Department said the Coalition's reform program - funded with $117 million in 2017 and another $124 million this year - was the most significant in the agency's 100-year history.

It has admitted that an outdated and complex compensation system has slowed the recovery of injured veterans and caused them unnecessary suffering. Advocates for ex-services personnel told the Productivity Commission it was too early to see the benefits of the changes. The Royal Australian and New Zealand College of Psychiatrists said more reform was needed.

The department said new technology for clients lodging claims online brought quick compensation decisions and had reduced more than 40 paper-based forms to between three to seven questions on the website. Veterans' Affairs identified the 40 most common conditions linked with military service, and has started making immediate decisions on claims related to those injuries without seeking more evidence.

Officials are creating a single IT system to replace 18 separate predecessors, which the department wants to decommission. The technology will improve how Veterans' Affairs processes claims, giving automatic alerts when milestones are missed.

"Improvements are providing faster access to treatment and compensation for veterans and their families," a spokesman said.

In another inquiry, run by former Attorney-General's Department secretary Robert Cornall, a Canberra-based veterans support centre said the department was still flawed in managing claims, particularly when rejections led to time-consuming reviews.

"It is of course recognised that some rejections may be valid but there are far too many that should have been simply found in favour of the claimant without the need for wasteful reconsiderations," the Veterans Support Centre in Belconnen said.

"Rather than acting in the best interests of the veterans, DVA staff often do not seem to accept the convention that where there is uncertainty or the validity of the case is finely balanced, a decision should favour the veteran."

The Royal Australian and New Zealand College of Psychiatrists warned veterans had reported encountering hostile bureaucrats with derogatory attitudes.

"The RANZCP stresses the importance of using language cautiously and judiciously when communicating with at-risk veterans and ex-service personnel."

The Veterans' Affairs Department has been the focus of several government inquiries amid rising frustrations over the compensation program. A national audit report this year found claims had been lost for up to 183 days, and a Senate inquiry urged the government to reduce backlogs. The Productivity Commission will publish interim findings in December, when Mr Cornall's scoping study will also deliver its report.