TORONTO -- If the Ontario government wants to shut down its coal plants by 2007, it must permanently sideline the restart of the Pickering A nuclear unit and instead focus on the construction of natural gas-fired plants and renewable energy facilities, says a report to be released Tuesday.

Although the report by the Ontario Clean Air Alliance gives the government a B-plus grade for taking steps to phase out the province's five coal-fired plants, it warns the government will only be falling into a sink hole if it continues with the rehabilitation of Unit 1 at the Pickering A nuclear reactor.

"Hopefully they will reject that recommendation because that could badly sidetrack the government and lots of money could be wasted on pursuing nuclear, which is the highest-cost and highest-risk option to phase out coal in Ontario,'' Jack Gibbons, chair of the alliance and an author of the report, said in an interview.

Ontario Power Generation has a dismal record for cost overruns and lengthy delays with its refurbishment of its nuclear reactors, says the report, a copy of which was obtained by The Canadian Press.

A decision by OPG's board about the reactor is expected in June, but the final decision will rest with Premier Dalton McGuinty and his cabinet, the report says.

The report also says it would be about 45 per cent cheaper to build a high-efficiency natural gas electricity generating plant than to spend about $500 million on the restart of Unit 1.

The alliance gives the government kudos for its call for 300 megawatts of renewable energy and 2,500 megawatts of conventional electricity, along with its promotion of energy conservation and its move to more realistic energy prices.

But there's still a long way to go before the government can make up the energy supply that will be lost by the closure of the polluting coal plants, the report says.

"There is no question that if the government doesn't pick up the pace of its actions in the next six months, it risks falling seriously behind and missing key opportunities to improve public health for the people of Ontario,'' Gibbons said.

The coal plants are one of the province's worst polluters.

The government has missed a number of key opportunities as it aims to shut the coal plants by 2007, the report says.

The government hasn't ordered the Independent Market Operator to develop an aggressive demand-response program -- such as paying major energy consumers like factories to curb use during peak hours in the summer.

The IMO would get the money back through its charges to market participants, and all businesses would benefit since electricity prices would drop along with demand, Gibbons said.

In the next six months, the government must move ahead on having smart electricity meters installed in homes so people can save money by conserving energy, the report says.