Liberal Leader Stephane Dion's proposed carbon tax plan is not ideal, but it's far better than what the current government has done to combat climate change, environmental groups said Thursday.

"If it's implemented I can see this plan making a tangible difference because it puts the machinery in place to reduce greenhouse gases,'' said Aaron Freeman, the policy director for Environmental Defence.

The Liberal plan proposes a $10-per-tonne price on greenhouse gas emissions, rising to $40 per tonne in the fourth year. At that point, the tax would be boosting federal revenues by $15.4 billion annually.

Environmental activists say while putting a price on carbon is a good symbolic gesture, those prices wouldn't necessarily be enough for a significant reduction in harmful greenhouse gases.

"Greenpeace and other environmental groups have been calling for virtually an immediate start at $30 per tonne of carbon dioxide equivalent, ramping up to $75 minimum within a decade,'' said Greenpeace climate and energy co-ordinator Dave Martin.

The lowballed price is one of the reasons Martin said Greenpeace is only offering "qualified support'' for Dion's plan.

"In our view the Dion plan really doesn't go far enough,'' he said.

A greenhouse gas reduction target of 20 per cent from 1990 levels by 2020 isn't high enough, the price is too low, and tax cuts that would go to lower-income Canadians under Dion's plan should instead be used to help Canadians conserve energy, Martin said.

"The devil's really in the details,'' he said.

But as many changes as Dion's plan would have to undergo to get an unqualified stamp of approval from Greenpeace, it is head and shoulders above what the current government is doing, Martin said.

"There's no question that the Harper government is way behind the curve in terms of doing anything about climate change,'' he said.

Martin said the Conservative government's plan for a 20 per cent reduction in greenhouse gases from 2006 levels by 2020 falls far short of Dion's proposed reduction from 1990 levels. In fact, he said the Harper government's reduction would only amount to a less than three per cent reduction from 1990 levels by 2020.

But the thrust of the Liberal plan is a positive symbolic gesture, one that is a good first step on the road to combatting climate change, said Graham Saul, the executive director of Climate Action Network Canada.

"Pricing carbon is a necessary building block of any meaningful climate change strategy,'' he said.

"Putting a price on carbon will encourage conservation. So this is going to move us in the right direction in terms of sending the right signals.''

Freeman also said he believes the plan would help change people's energy consumption habits, especially with a higher price on carbon.

"Certainly having that carbon price go up at a significant enough rate is going to have an impact on how much people conserve and how much greenhouse gas emissions will go down,'' he said.

Meanwhile, Nova Scotia Premier Rodney MacDonald is reluctant to embrace Dion's proposal even though the notion of a carbon tax figures into his own government's climate change policy deliberations.

"I'm certainly not in favour of increasing the energy pressures on Nova Scotians either at the pumps or for home heating,'' he said as he emerged from cabinet on Thursday.

"Given the situation that we're in where there's a strong reliance on fossil fuels in Nova Scotia, a plan like that could have a significant impact on those on fixed incomes and seniors.''

B.C. Energy Minister Richard Neufeld said he was wary of the proposal, expressing concerns any sweeping federal plan could encroach on provincial territory. But he noted the Liberals are not in power, so it won't necessarily be implemented.

"I know with the Conservatives, they've told us that if they were to bring in a carbon tax or any kind of a tax on carbon they wouldn't double it in provinces that already have those kind of taxes in place,'' he said.

"I would hope to think, depending on elections, that the federal Liberals would be the same.''