Five years since allegations were first made against Thomson, and after the former MP's constant denials, his lawyer admitted in Melbourne Magistrates Court his client used Health Services Union funds to pay for sexual services while he was the union's national secretary between 2002 and 2007.

But Greg James, QC, said Thomson should be spared a jail term given the humiliation he had already suffered and because a stint behind bars would be onerous for a man with health problems, including depression, and a young family and who had spent much of his life serving the public.

Mr James said Thomson had agreed to repay the HSU the $24,538.42 he embezzled with union-issued credit cards and a Flight Centre account, and was prepared to travel from his NSW home to perform community work in Victoria.

But lead prosecutor Lesley Taylor, SC, said Thomson only deserved jail for his ''continuous and sustained breach of trust'' and for conduct that had been ''arrogant in the extreme''.

Ms Taylor said Thomson had ''uttered not a single word of remorse'', despite being found guilty of offences that not only betrayed the HSU and its members but was ''contemptuous of the entire union movement''.

Outside court, HSU officials Kathy Jackson and Marco Bolano - who were among those to first learn of Thomson's rorting after an exit audit was performed when he left the union to become the Labor member for the NSW seat of Dobell - echoed the prosecutor's call.

Mr Bolano, who at one point found himself seated next to Thomson because of the scarcity of spare seats in court, said his former colleague had ''smashed'' the union movement's reputation through his actions and deserved jail.

''Given his position, given this pantomime, this charade that's gone on for four years and his … cynical lying,'' he said. ''There's no remorse, I don't think there are any mitigating circumstances. I think he should do time,'' he said.

Mr Bolano said Thomson's conduct in denying the accusations - under the protection of parliamentary privilege in 2012, he famously accused Mr Bolano of setting him up - had put an enormous strain on him, his family and his own career.

Ms Jackson described Thomson's offences as ''obscene'' and said she looked forward to the royal commission into union affairs weeding out the corruption that protected Thomson and former HSU president Michael Williamson, who defrauded the union of almost $1 million and will be sentenced next week.

Thomson, 49, will be sentenced on Tuesday. He faces a maximum jail term of five years after he was found guilty of 65 fraud and theft offences last month.

Magistrate Charlie Rozencwajg found Thomson guilty of using HSU funds for sexual services, of making cash withdrawals with his union-issued credit card and buying cigarettes and firewood for his then wife with union money.

He was also found guilty of using union funds after he had quit the HSU and become an MP, and guilty of some charges related to paying for travel expenses for his then wife.

But some of the charges related to spousal travel were dismissed, as were the charges related to buying in-house movies at hotel rooms while on work trips.