The Ontario Liberals say they will expand the Greenbelt if they form government in June, the party announced Wednesday.

The commitment comes one day after PC Leader Doug Ford walked back a proposal to develop "chunks" of the Greenbelt to help ease the housing affordability crisis in the GTA and surrounding areas.

The 7,200-square-kilometres, or more than two millions acres, of environmentally-sensitive land spanning the Golden Horseshoe area around Lake Ontario was protected through legislation in 2005.

Premier Kathleen Wynne said the expansion will be part of the Liberals official campaign platform, which has not been released. However the backbone of the expected platform was already revealed in the 2018 provincial budget.

According to Wynne, the Greenbelt would grow to include areas such as:

Waterloo and Paris/Galt Moraine.

Orangeville Moraine.

Oro Moraine.

Nottawasaga River corridor.

A release outlining the expansion also says that "additional wetlands and small moraines" in Dufferin and Simcoe counties could be included as well.

Ford made his initial comments at an event he attended while running to be PC leader in February. A video tape of his address to an audience that reportedly included developers was posted online from an anonymous account. The provenance of the video is unclear.

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On Tuesday afternoon, however, Ford released a statement promising to preserve the Greenbelt "in its entirety" should he be elected premier in the June 7 election. He added that he was focused on building more houses, but has since rethought his proposal.

"The people have spoken — we won't touch the Greenbelt. Very simple. That's it, the people have spoken. I'm going to listen to them. They don't want me to touch the Greenbelt, we won't touch the Greenbelt."

Speaking to reporters beside the Humber River in Toronto, Wynne used the announcement to go on the offensive against Ford, suggesting that he only abandoned the proposal because it became public.

"A growing Greater Toronto and Hamilton area needs a growing Greenbelt. Not one that is being cut up and sold off to the highest bidder," she said.