The assistant treasurer, Stuart Robert, joined a business selling cryotherapy with a man who had just been convicted of raping an adult dancer, documents show.

Robert, who is now facing scandals on multiple fronts, became a director of alternative health firm Cryo Australia in mid-August, but left two and a half weeks later, shortly after his appointment to the newly-formed Morrison ministry.

The franchise business was set up in 2016 by founder and director Neranjan Agrajith Kalubuth De Silva, 31, who marketed cold air cryotherapy to treat a range of ailments, including fatigue, sore muscles, “dull” skin, cellulite, and acne.

At the time Robert joined the firm, De Silva was before Queensland’s highest court appealing against a rape conviction, Guardian Australia can reveal.

Two months earlier, De Silva had been found guilty and sentenced in the Queensland district court for sexually assaulting an adult dancer who had been sleeping on the couch of a mutual friend’s house in the Brisbane suburb of Fortitude Valley on 30 May 2016.

De Silva was charged soon after the incident and bailed a few days later, before spending six months in immigration detention “as a direct result of being charged”, according to court records. His appeal against the conviction ultimately failed.

De Silva is still listed as Cryo Australia’s secretary and director in documents lodged with the corporate regulator. He is still described on the company’s website as “director & founder” and says he is Cryo Australia’s managing director on his LinkedIn page.

A spokesman for Robert told Guardian Australia the assistant treasurer was: “only involved with Cryo from a commercial perspective that was all declared to the parliament”.

“Mr De Silva did not disclose his conviction during corporate due diligence and Mr Robert did not know of it until informed now,” the spokesman said.

The revelations raise further questions about Robert’s business dealings, which are already the subject of an investigation by the the Australian Securities and Investments Commission (Asic).

Asic is investigating whether Robert breached the Corporations Act by failing to give timely notification to the regulator that he had resigned as a director of Cryo Australia. He denies any wrongdoing and says he provided proper notice to the company, which bears responsibility for advising Asic.

Robert’s involvement with Cryo Australia adds to a string of recent scandals. Last month, he drew intense criticism for an exorbitant internet bill, which he charged to taxpayers at a rate of $2,000 per month. Robert blamed “connectivity issues” at his home and has since paid back the money.

In 2016, Robert was dumped from the ministry by the former prime minister Malcolm Turnbull for a scandal over a “private” trip to Beijing. Robert had attended an event in China to preside over a deal involving an Australian mining company headed by a Liberal party donor. He had an indirect financial stake in the company.

The head of the Department of the Prime Minister and Cabinet, Martin Parkinson, found Robert had “acted inconsistently” with the statement of ministerial standards.

Guardian Australia has made repeated attempts to contact De Silva and Cryo Australia in recent weeks.

No one answered the door at De Silva’s residence, and staff at Cryo Australia’s listed principal place of business told Guardian Australia they could not assist.

Emails and calls to De Silva, as well as his associates, went unanswered. His email out-of-office message says he is “currently overseas for a personal matter” and his mobile is switched off.

De Silva describes himself as a doctor on the website of Cryo Australia and its parent company, Global Health and Wellness Group. His LinkedIn page says he has medical qualifications from the University of Queensland, Griffith University and Queensland University of Technology.

Guardian Australia found no reference to De Silva on the Australian Health Practitioner Regulation Agency’s (AHPRA) register of medical practitioners. The register lists all qualified health practitioners registered to practise in Australia.

AHPRA confirmed it could find no reference to De Silva in its own searches of the register.

Neither does De Silva appear in the online graduate verification systems of University of Queensland or Griffith University. The Queensland University of Technology lists him as graduating with a Bachelor of Applied Science (Biochemistry) in 2011.

It is not an offence to call yourself a doctor without medical qualifications. De Silva might have graduated elsewhere to justify his self-description of “doctor”, and he and his associates have not answered questions about his education and qualifications.

De Silva had vigorously denied the sexual assault allegation. In an interview with the police, he said he had never digitally penetrated the woman, as she had alleged. He claimed she had come on to him but he told her he had a girlfriend.

“I said I’ve got a girlfriend and, and I went this and that, and then she sort of freaked out,” De Silva told police, according to court documents.

“Like I don’t know if she freaked out or did what and she just sort of started yelling and things, and, and now I, and I s-, I called my mate [name redacted], and I just said I can’t stay here and I left, and I don’t know what happened after that, until you guys just, yeah and so.”

In her evidence to the court, the woman said she had fallen asleep on the couch at her friend’s home in Fortitude Valley after a night out in May 2016. De Silva, who she had previously known, was also staying at the home.

She said she woke to her underwear being removed and De Silva digitally penetrating her.

A jury found De Silva guilty of one charge of rape but acquitted him of another. He was initially sentenced to two years’ imprisonment, suspended after eight months. That sentence was reduced on appeal to 18 months, suspended after six months. De Silva had already spent six months in immigration detention, court documents show.