TORONTO -- Doug Ford said Monday he would allow some development in the Greenbelt -- the world's largest permanently protected green space -- if elected premier this spring, to ease the housing crisis in the Greater Toronto Area.

The Progressive Conservative leader made the comments after the governing Liberals accused him of making private deals with developers to open up the Greenbelt for housing development.

The Liberals pointed to an online video of Ford -- apparently taken in early February when he was a Tory leadership candidate -- promising to open up a "big chunk" of the protected area.

When asked Monday about the video, Ford said he supports the protected green space but would allow development in some areas to create more supply in the housing market, including more affordable housing.

"I support the Greenbelt in a big way," he said. "Anything that we may look at to reduce housing costs, because everyone knows housing costs is through the roof and there's no more property available to build housing in Toronto or the GTA."

For every piece of the Greenbelt opened for development, Ford said he would add equivalent land to the protected area to ensure it doesn't change in size, but he didn't offer details on how that would work.

"I give you my commitment, that anything that we look at on the Greenbelt will be replaced," he said. "So, there'll still be the equal amount of Greenbelt."

Ford said the only way to bring down housing costs in the Toronto region and make the market more affordable is to increase the supply.

"You build more and hopefully it will level off," he said. "But it's a tough situation right now."

In the 40-second video clip, which was posted Monday on YouTube, Ford suggests the idea of opening the Greenbelt for construction came from developers.

"I've already talked to some of the biggest developers in this country, and I wish I could say it was my idea, but it was their idea as well," he said. "Give us property and we'll build and we'll drive the cost down."

Environment Minister Chris Ballard, who represents a riding that is home to part of the protected area, accused Ford of quietly planning to pave over it.

"(It's) a plan he has kept from the public but shares privately ... with developers who stand to make big money if Ford wins," he said.

Ballard said the Greenbelt, a 7,200-square-kilometre area that borders the Greater Golden Horseshoe area that surrounds Lake Ontario, must continue to be preserved.

"(Ford) will bulldoze a great swath of the Greenbelt and turn it into the largest condo farm this province has ever seen," he said.

The Greenbelt, established in 2005, protects environmentally sensitive land and farmlands from urban development.

"We moved to protect it forever so that our kids and grandkids would never have to worry about having access to nature and that we would have productive farm lands well into the future," Ballard said. "So, it's essential this area stay protected."

NDP environment critic Peter Tabuns said Ford's plan will plow over farms, forests and green spaces. An NDP government would protect the Greenbelt from land speculators, he said in a statement.

"When it comes to creating a livable, affordable province, Doug Ford is saying one thing publicly and another in private to his big, rich developer friends," Tabuns said. "New Democrats support Greenbelt policies that protect natural heritage while encouraging affordable, transit-friendly 'complete communities."'

Joe Vaccaro, CEO of the Ontario Home Builders' Association, said there is a government process that developers respect and follow when it comes to the Greenbelt, and changes to the legislation do no happen in secret.

"(The government has) made some adjustments to the Greenbelt boundary based on scientific information and infrastructure information," he said. "Adjustments do happen. It's part of the process. More importantly, this all happens through a public, transparent, accountable structure."