OTTAWA — Prime Minister Stephen Harper's government is in the dark about the economic costs of its climate change policies and needs to carefully weigh the risks of scaling back federal oversight of industrial development, warned Parliament's environment watchdog Tuesday.

Scott Vaughan, the federal commissioner of the environment and sustainable development, made the comments after tabling an audit in Parliament that concluded Canada was "unlikely" to meet Harper's own climate change goals while it faced a $7.7-billion liability over sites that were mostly contaminated decades earlier during an age of weak environmental oversight.

"We cannot go back and repeat the errors of the past," said Vaughan at a news conference. "I don't think that Canadians can afford it and I don't think they would actually accept it."

In the House of Commons, Harper said his government had made "record investments" to clean up sites neglected in the past, while "ensuring that we have thorough environmental assessments going forward." The government's recent budget legislation proposes to rewrite or weaken several Canadian environmental laws, downloading some of the responsibilities to the provinces.

Environment Minister Peter Kent agreed with the importance of sharing information about costing of measures but said it would be "premature and speculative" to do so prior to consultations with industries such as the oil and gas sector, which do not yet face federal regulations cracking down on greenhouse gas (GHG) emissions.

NDP deputy leader Megan Leslie noted that Vaughan's report suggested the government's lack of research contradicts its own arguments it is withdrawing from the international Kyoto Protocol on climate change to protect the Canadian jobs and industry.

"One would think if (remaining in the Kyoto agreement) was too costly, there would be numbers for their current plan," Leslie said. "But they (numbers) don't exist. They're working in some sort of fiction world."

Vaughan said his office expected that the government would analyze these costs to implement an effective plan to reduce the emissions that trap heat in the atmosphere and contribute to global warming. But its current approach of introducing regulations, one sector at a time, is incomplete and has not even analyzed whether the government's goal of aligning policies with the United States would be cost-effective, the audit said.

So far, he noted, the government has only brought in two regulations to control emissions in the transportation sector. Rules to govern emissions in the electricity sector have not been finalized and would not take effect until 2015. Furthermore, there are absolutely no regulations in place to slash pollution from oil-and-gas companies.

"We found that this approach lacks an overall implementation plan designed to achieve the 2020 target, as well as economic analysis to estimate what the approach will cost the Canadian economy," said the audit.

"Without an implementation plan, industry, consumers and other levels of government lack a solid basis for knowing how to adjust technology and make normal investment decisions."

His report said it was "unlikely" the government can implement a plan in time to meet Harper's target of reducing annual emissions by 17 per cent below 2005 levels by 2020.