A leading Canadian psychiatrist who kept accusations of gross human rights abuses in apartheid-era South Africa hidden has been charged in Calgary with sexually abusing a male patient and is being investigated over dozens of other allegations.

Dr Aubrey Levin, who in South Africa was known as Dr Shock for his use of electricity to "cure" gay military conscripts, was arrested after a patient secretly filmed the psychiatrist allegedly making sexual advances. Levin, who worked at the University of Calgary's medical school, has been suspended from practising and is free on bail of C$50,000 (£32,000) on charges of repeatedly indecently assaulting a 36-year-old man.

The police say they are investigating similar claims by nearly 30 other patients. The Alberta justice department is reviewing scores of criminal convictions in which Levin was a prosecution witness.

Levin has worked in Canada for 15 years since leaving South Africa, where he was chief psychiatrist in the apartheid-era military and became notorious for using electric shocks to "cure" gay white conscripts. He also held conscientious objectors against their will at a military hospital because they were "disturbed" and subjected them to powerful drug regimens.

South Africa's Truth and Reconciliation Commission heard that Levin was guilty of "gross human rights abuses" including chemical castration of gay men. But after arriving in Canada in 1995 he managed to suppress public discussion of his past by threatening lawsuits against news organisations that attempted to explore it.

Following the arrest, other male patients have contacted the authorities. One, who was not identified, told CTV in Canada that he had gone to Levin for help with a gambling addiction and alleged he had been questioned about his sex life and subject to sexual advances.

The arrest has raised questions about how Levin was allowed to settle in Canada. Canada admitted other South African medical practitioners accused of human rights abuses, including two who worked with Wouter Basson, known as Dr Death for his oversight of chemical and biological warfare experiments that included the murder of captured Namibian guerrillas.

Levin, who made no secret of his hard rightwing views and was a member of the ruling National party during apartheid, has a long history of homophobia.

In the 1960s, he wrote to a parliamentary committee considering the abolition of laws criminalising homosexuality saying that they should be left in place because he could "cure" gay people.

His efforts to do just that in the army began in 1969 at the infamous ward 22 at the Voortrekkerhoogte military hospital near Pretoria, which ostensibly catered for service personnel with psychological problems. Commanding officers and chaplains were encouraged to refer "deviants" for electroconvulsive aversion therapy.

The treatment consisted of strapping electrodes to the upper arm. Homosexual soldiers were shown pictures of a naked man and encouraged to fantasise, and then the power was ratcheted up.

Trudie Grobler, an intern psychologist on ward 22, saw a lesbian subjected to severe shocks.

"It was traumatic. I could not believe her body could handle it," she said later.

One gay soldier claimed to have been chemically castrated by Levin. The Truth and Reconciliation Commission was told by investigators that he was not alone. It also heard that at least one patient had been driven to suicide. Levin refused to testify before the commission.

Levin also treated drug users, principally soldiers who smoked marijuana, and men who objected to serving in the apartheid-era military on moral grounds, who were classified as "disturbed".

Levin subjected some patients to narco-analysis or a "truth drug", involving the slow injection of a barbiturate before the questioning began. In an interview with the Guardian 10 years ago, he did not deny its use but said it was solely to help soldiers suffering from post-traumatic stress.

Levin said he left South Africa only because of the high crime rate, and denied abusing human rights. He said electric shock therapy was a standard "treatment" for gay people at the time and those subjected to it did so voluntarily.

"Nobody was held against his or her will. We did not keep human guinea pigs, like Russian communists; we only had patients who wanted to be cured and were there voluntarily," he told the Guardian in 2000.