OTTAWA - A draft climate plan being considered by the federal government would weaken the long-term goal for cutting greenhouse emissions from what was announced by former environment minister Rona Ambrose last October.

Under the federal draft plan, marked secret and dated April 13, the government would undertake to cut emissions 45 to 65 per cent from 2006 levels by 2050.

Ambrose's plan, in the original version of the Clean Air Act, used an earlier base year when emissions were lower to calculate cuts. That plan would have cut emissions 45 to 65 per cent from 2003.

Since emissions have risen significantly since 2003, the shift in base year results in a less stringent target.

The Clean Air Act met with widespread criticism because its targets were considered too weak. Environmentalists pounced on the indication that they might be weakened further in the new plan being considered.

"We need to constantly pay attention to the base year,'' said Green Party Leader Elizabeth May at a news conference Tuesday.

"They have actually weakened the target Madame Ambrose announced last fall with the Clean Air Act, which is actually a target for a shrinking Great Lakes, disappearing Arctic ice, storms on our coasts and a dust bowl on our prairies.''

After ignoring environmental issues during last year's election campaign, the Conservatives did an about-face in December and made reducing the greenhouse gases that cause climate change a top government priority.

Pollsters have said the Conservatives' success in convincing Canadians of the sincerity of their conversion to green will be key to their re-election effort.

A spokesman for Environment Minister John Baird would not comment specifically on the draft plan beyond saying that details of the government's program will be announced soon.

Many scientists say greenhouse gas emissions need to be cut 80 per cent by 2050 to avoid dangerous climate change.

Environmentalist say the Conservative draft plan doesn't go nearly far enough.

"You have a target that wasn't strong enough to begin with and they've weakened it even more and they think Canadians won't care,'' said Louise Comeau of the Sage Centre, an environmental think tank.

"We're not even close  to what scientists are saying is needed.''

The draft federal plan says that the rapid growth in emissions will stop by 2012 and total emissions will be 20 per cent below 2006 levels by 2020.

The document provides no breakdown to indicate which programs and regulations will ensure the promised emissions reductions.

Sources close to the oil and gas industry said the plan has angered industry officials because it places most of the burden on big polluters, without significant demands on consumers who account for half of emissions.

The plan contains no carbon tax nor firm "hard cap'' on greenhouse emissions. Instead it depends on intensity targets, which would allow emissions to continue rising along with industry output.

Companies who couldn't meet their targets under the draft plan would be allowed to pay into a technology fund to develop emissions-cutting technologies.

But their ability to use that fund would ratchet down over time, forcing them cut their own emissions rather than just buying credits.

Some economists maintain that the Kyoto target is impossible without spending huge amounts on the purchase of international emissions credits.

Mark Jaccard of Simon Fraser University says his economic models show that meeting Kyoto targets this way would be prohibitively expensive.

"I think any funneling of large amounts of money overseas would be politically impossible,'' he said.

The government is expected to produce an analysis soon showing that the Kyoto targets are unachievable without widespread damage to the economy.

But environmentalists continue to insist that the Kyoto targets can be met, as shown by a number of European countries that are on track to meeting them.

"We demand a Kyoto plan, nothing else will do,'' said John Bennett of ClimateforChange, a new environmental group.