The lawyer representing two women who underwent operations at the Lachine hospital says its negligence caused them "anxiety, stress and fear."
David Assor says the hospital did not properly clean a piece of equipment between operations and exposed up to 150 former patients to risks of contacting HIV, hepatitis and other viruses.
The instrument is a liver retractor, used mainly in bariatic surgery.
The hospital sent out letters to its patients in April informing them that they may be at risk and urged them to come in for blood testing.
One of Assor's patients, who was operated on in February 2013, was tested and her results were negative. The other, who was operated on in February 2014, is still waiting for a second test.
Assor added that the treatment his patients received inappropriate treatment at the testing clinic, with staff asking personal questions about their sex lives. He said it seemed as if the hospital was trying to shift the blame if any tests came back positive.
And while some patients' rights advocates have praised the hospital for coming forward, Assor notes that it only sent out letters to patients and did not bring the matter to the public via the media.
As a result, an estimated 11 per cent of patients at risk have not been contacted, he says. He urges anyone who thinks they may qualify to pariticipate in the suit to contact him via his law firm, Lex Group Attorneys.
No amount has yet been specified for the suit, which is asking for moral and punitive damages.
He estimates the entire process may take up to four years.