Bruce McArthur, a 67-year-old landscaper, killed eight men with ties to Toronto's gay village. (Facebook)

LGBT activists are calling for “an immediate inquiry” into police conduct around an alleged gay serial killer in Toronto.

The group, which launched an initiative called Toronto’s Missing and Murdered Rainbow Community Members, are asking police “what went wrong” following the arrest of alleged serial killer Bruce McArthur.

McArthur is accused of killing seven men around the Toronto area and disposing of their bodies in plant pots.

“Our community is grieving, our community is angry,” Douglas Elliott, a lawyer and community member said at a press conference.

“As recently as last December we were being told by Chief Saunders that our long standing concerns about a serial killer preying on our community were not based on any evidence. He was wrong.”

Earlier this month an internal investigation was reportedly launched over allegations of police misconduct in the Bruce McArthur case.

Mr McArthur stands accused of killing seven men he met in Toronto’s gay district and on gay dating apps.

The lead detective investigating the case has uncovered possible misconduct by police in a “troubling” incident involving the alleged serial killer years before he was arrested.

The incident is now the subject of a formal investigation by officers, according to The Globe and Mail.

Homicide Detective Sergeant Hank Idsinga said he came across details of possible misconduct in mid-2017, but has only been able to compile the full details in recent weeks.

A formal dossier was reportedly handed to police.

Det. Sgt. Idsinga was asked by local news if the investigation was “a career case” for him and his colleagues.

“This one is certainly going to have an impact on some careers, positively and possibly negatively as well, but it’s definitely one for the books,” he replied.

66-year-old Mr McArthur was charged with a sixth murder, of Skandaraj Navaratnam, 40, last month.

Navaratnam went missing in 2010, making him one of a string of men who disappeared from Toronto’s gay village downtown.

Officers have confessed that there could be more victims of the alleged killer and have searched 30 separate sites.

McArthur worked as a landscape gardener and police fear there could be the remains of more men in gardens around the city.

McArthur has not yet entered a plea to any of the charges thus far.

Police are still working to identify the remains of people who were found inside planters.

Haran Vijayanathan, a community activist and executive director of the Alliance for South Asian AIDS Prevention in Toronto, believes that authorities missed vital clues to the alleged killer in early years.

“Until that point, all the South Asian men that went missing kind of fell by the wayside and nobody paid attention until something happened in the white community,” he said.

McArthur has also been charged with the murder of Selim Even, Andrew Kinsman, Majeed Kayhan, Soroush Marmudi and Dean Lisowick – all of whom had connections to the city’s gay scene.