Mark Grant says having to speak to 60 welfare claimants a day, who "pulled at his heartstrings" with the stress of the experience, left him with "telephone phobia" and unable to earn a living.

The former Department of Human Services public servant told the Administrative Appeals Tribunal that his six months at Centrelink in 2008 felt like a long time.

He detailed for the tribunal daily conversations he found stressful: "Young people who were unable to get jobs pulled at his heart strings, people would say they were unable to pay the rent, let alone pay to travel to a job interview; people who were relying on the generosity of friends."

Mr Grant told tribunal member Naida Isenberg there was also an element of aggression in some of the calls, although she said there was no evidence he complained to his bosses about any specific threats or abuse.

In the claim form he submitted to federal workplace insurer Comcare, Mr Grant said the cause of his illness was "a combination of so many people living in despair; so many people 'ripping off the system'; the system being unfair/rigid."

He said his illness was caused by "taking of telephone calls, fear of what/who the next call might be".

"Young homeless people hit [him] the hardest," the judgement said.

But Mr Grant's claim, lodged in May 2013, more than four years after he left his Human Services job, was complicated by the fact that he was running a mortgage broking business employing up to 10 people while he worked at the welfare agency.

After the business went bust in 2009, Mr Grant relied on his income protection insurance until it ran out and then made an unsuccessful application to his old employer, Centrelink, for a disability support pension before approaching Comcare with his worker's compensation claim.

When Comcare rejected the claim, he took his case to the tribunal, where he said he now worked driving a taxi and that he did not use the phone to take bookings, but relied instead on the network computer.

The tribunal read two reports from psychologists and one from a psychiatrist, which attributed Mr Grant's mental problems to the failure of his mortgage broking business.

In her ruling, Ms Isenberg noted that to be eligible for Comcare's generous benefits, Mr Grant had to prove that Centrelink contributed to his illness to a "significant degree".

"The medical evidence, from the medical practitioners with whom the applicant consulted, does not attribute the applicant's psychological condition to his Centrelink workplace at all, let alone to a 'significant degree'," Ms Isenberg wrote.