Real estate insiders say a foreign buyers' tax aimed at cooling British Columbia's red-hot real estate market could end up hurting locals if it leads to purchasers walking away from deals that are already in the works.

The B.C. government is poised to adopt legislation that would put an additional 15 per cent property-transfer tax on foreign nationals who buy residential real estate in Metro Vancouver.

Bob de Wit, who heads the Greater Vancouver Homebuilders' Association, says there's a lot of concern among foreign buyers who signed pre-sale agreements that aren't due to close until after the tax becomes law next Tuesday.

De Wit estimates there are 2,300 properties in Metro Vancouver that are connected to foreign buyers.

He is encouraging the government to exempt deals already in the works before next week's implementation of the tax.

Premier Christy Clark says she's not open to amending the legislation, saying the law is designed to make housing more affordable for the middle class.

Canada Mortgage and Housing Corporation rang alarm bells in a report earlier this week about Vancouver's housing sector, upping the city's risk rating to its highest level for the first time since it began releasing reports last year.