Ontario New Democrats asked the auditor general's office on Friday to launch a new investigation of the government's land-use policies by probing its expansion of some municipal boundaries.

NDP Leader Marit Stiles and two other caucus members said in a letter to the acting auditor general — Bonnie Lysyk's term expired and the province has not yet named a new auditor general — that the request follows the office's "explosive" Greenbelt report that found the process to select lands for removal from the protected area favoured certain developers.

Premier Doug Ford ultimately reversed his Greenbelt plan after that report and another one from the integrity commissioner, which made similar findings.

The NDP claimed there is evidence that preferential treatment was given in the urban boundary expansions — against the wishes of some affected municipalities — to some of the same developers that stood to benefit from the Greenbelt land removals.

"These forced urban boundaries are the other half of Ford's Greenbelt scheme that benefited wealthy land speculators," said Sandy Shaw, who represents Hamilton West-Ancaster-Dundas.

"I call on Ford to do the right thing and respect the decisions of our Hamilton council and community by cancelling this plan."

CBC has reported that in Hamilton, land added to the city's urban boundary for growth contains properties owned in part by two developers with lands in the Greenbelt parcels in question.

A spokesperson for Municipal Affairs and Housing Minister Paul Calandra said the province will continue to "take decisive action" to ensure municipalities can meet their housing targets.

"The province follows a standard official plan review and amendment process that is open to the public and which has the goal of ensuring municipalities are properly prepared to accommodate growth," Alexandru Cioban wrote in a statement.

"In the case of Hamilton and Waterloo, the municipalities chose to ignore their own staff recommendations, which found that existing urban boundaries must be expanded in order to meet long-term housing needs."

The NDP is asking the office to conduct a value-for-money audit and assess the financial and environmental impacts of the government's changes to municipal official plans for Hamilton, Ottawa, Waterloo, York, Peel, Niagara, Peterborough, Halton and Wellington, as well as Ministerial Zoning Orders, which override local zoning bylaws.

"We ask that your office specifically consider whether such decisions were evidence-based and consistent with provincial plans, policies and statutes, as well as their impact on the smooth functioning of municipal and provincial planning and approval processes," the NDP wrote.

"We also ask that you investigate whether the decision-making process adhered to standards of conduct expected of officials in a position of public trust, including standards concerning conflicts of interest and preferential treatment. Finally, we also ask that you determine how much wealth was transferred to affected property owners as a result of such decisions, and whether this transfer was in the public interest."

Lysyk found in her Greenbelt investigation that more than 90 per cent of the land removed was in five sites passed on to then-housing minister Steve Clark's chief of staff, Ryan Amato, by two developers Amato met at an industry event.

The property owners with land removed from the Greenbelt stood to see their land value rise by $8.3 billion, the auditor general found.

The integrity commissioner said in his August report that he had no evidence of developers being specifically tipped off that the government was considering Greenbelt removals — though he found one developer "questionable" on that point — but that Amato's actions and conversations with them had that effect.

Clark and Amato have both since resigned.

The RCMP is reviewing information to determine whether it should investigate the Greenbelt land swap. Ford has said he is confident nothing criminal took place.