Open this photo in gallery Ontario NDP Leader Andrea Horwath. Galit Rodan/The Canadian Press

An NDP government in Ontario would introduce a series of new accountability measures surrounding party nominations and government procurement, Leader Andrea Horwath announced Friday.

She made the promise after the release of a Globe and Mail investigation that focused on how Spiros Papathanasakis, an unregistered lobbyist, was able to influence public institutions, including senior officials at Queen’s Park. The investigation detailed a 2013 meeting between a Liberal infrastructure minister, Glen Murray, and Marolyn Morrison, where the then-mayor of Caledon, Ont., said she faced pressure to support a residential development near her town, which she says she refused.

Ms. Horwath sent a letter to Ontario’s Integrity Commissioner on Friday morning, asking the office to probe the findings of The Globe’s investigation. Speaking with reporters during an event in Liberal Leader Kathleen Wynne’s Toronto riding, Ms. Horwath said she will ask the Ontario Provincial Police to look into whether any laws were broken in procurement practices and “allegations of threats made to and by elected officials.”

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Should the New Democrats win office after the June 7 election, Ms. Horwath said she would call for an all-party committee to look into the situation. She said that committee would be modelled on one that looked into former premier Dalton McGuinity’s decision to cancel two natural gas power plants.

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Mr. Murray stepped down as an MPP in 2017 to become the executive director of an environmental think tank in Alberta. He has disputed the former mayor’s characterization of the meeting and described it as “pleasant.”

Ms. Morrison said she brought her concerns to Ms. Wynne after the incident in 2013. On Thursday, Ms. Wynne told reporters that she did not recall the situation: “I don’t recall a contentious exchange with Glen Murray, I just don’t recall,” she said.

The Progressive Conservatives declined to comment on The Globe’s investigation.

With her party effectively tied with the Tories in most polls and the Liberals unlikely to form government, Ms. Horwath said that Ontarians still deserve an explanation of what happened.

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“When you have a minister of the Crown being alleged to be engaged in this sort of activity and alleged to be intimidating a mayor of a municipality for the purpose of greasing the wheels for a property development, and then you have a premier who is accused of not acting on those allegations, those are some pretty serious problems and I think if the OPP sees fit, that would be a good place for them to spend some time,” Ms. Horwath said.

The NDP would also ask Elections Ontario to call for independent experts to make recommendations on how the agency could introduce rules to oversee the nomination of candidates by the province’s political parties. The Progressive Conservatives, under Leader Doug Ford and his predecessor, Patrick Brown, have been dogged by nomination troubles for nearly a year.

Police in Hamilton are investigating accusations of ballot-stuffing at a Tory nomination in that city, while police north of Toronto are looking into a data breach at the company that operates the 407 toll highway. A PC candidate who worked for the toll highway resigned immediately after the company reported the data breach and has denied any wrongdoing.