Niagara region police say Kormos, 60, died Saturday morning at his home in Welland, Ont. The cause of death was not immediately known.
NDP Leader Andrea Horwath says Kormos was a personal mentor who was relentless in his advocacy for Ontarians, especially those in contact with the justice system.
"He knew what he was there to do, which was stick up for the little guy and fight for everyday folk," she said.
After ending a 23-year-stint at the legislature in 2011, Kormos was elected last year to represent Welland on Niagara Regional Council.
Coun. Andrew Petrowski, who co-hosted a radio talk show with Kormos, said he was a force to be reckoned with in the council chamber.
"When Peter stood up nobody in council, including the chair, could control him. He was in control of that council and he would get his thought across come heck or high water," he said.
Premier Kathleen Wynne tweeted her condolences.
"Peter Kormos was a supportive friend, and I will miss his presence and his profound understanding of parliamentary procedure."
A criminal lawyer by trade, Kormos was first elected to the legislature in 1988.
He was named to cabinet when the New Democrats surprisingly swept to power under Bob Rae in 1990.
But Kormos, known to speak his mind, feuded with Rae over public auto insurance, which Kormos pushed for but the government never went ahead with.
Kormos was a bombastic speaker and didn't shy away from antics in the legislature, such as an all-night speech on the insurance issue. His staple outfit consisted of a collared shirt and cowboy boots.
A series of events including his posing, fully clothed, as a "Sunshine Boy" in the Toronto Sun newspaper led to his removal from cabinet in 1991.
"Mr. Rae blessed me by creating that distance between me and him. It guaranteed that I got re-elected in '95," Kormos told The Canadian Press before his retirement in 2011.
Rae remembered Kormos as someone who always stood up for what he believed in.
"I remember him as a man of passion and great determination. He became a fierce critic of mine, but that happens in life and politics, and I know he continued to have a real impact at Queen's Park and in the Niagara region," Rae said in an email.
Kormos was prone to witty hyperbole in the legislature, comparing former Liberal premier Dalton McGuinty to Pontius Pilate for trying to oust the province's ombudsman. As a lawyer, Kormos knew how to walk the fine line between outrageous put-down and slander.
Kormos was deeply passionate about human rights and social justice, and spoke strongly against the governing Liberals over a secret law they passed giving police powers to detain and arrest people during the Toronto G20 summit in 2010.
In a statement, Tory Leader Tim Hudak said Kormos was a one-of-a-kind politician, but one who dropped his partisanship at the door on his way out of the legislature.
"It's rarely said — and in the best sense of the phrase — by politicians these days when speaking of someone so diametrically opposed in beliefs and convictions, but I can say with sad confidence on this day, 'We shall not see his like again."
— By Will Campbell in Toronto
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