NDP leader Carole James will oppose B.C.’s new carbon tax even if the Liberals add the element she says is missing from their plan: a tougher crackdown on emissions from heavy industry.

Speaking Monday at a roadside rally in Surrey, James denounced the carbon tax as one that will let the biggest polluters off the hook while penalizing ordinary motorists.

“We need more than simply an unfair gas tax,” she said as placard-waving NDP MLAs got honks of support from motorists.

But she said she’d still oppose the tax even if a promised cap-and-trade system for big emitters is created.

“You can’t just completely tax people,” James said. “Families are already struggling, they’re already paying more and they see that every day.”

The street corner rally in Cloverdale took place in the constituency of transportation minister Kevin Falcon, who James challenged to defend the government’s policy.

New Democrats hope to force premier Gordon Campbell to back down from the carbon tax in the face of public anger over high gas prices – which will be bumped up another 2.4 cents July 1 by the new levy – or else capitalize on public anger in next May’s provincial election.

James insisted the carbon tax won’t work, although it’s supported by a coalition of environmental groups.

“Even the government’s own advisers say at most it’s going to decrease emissions by two per cent by the year 2020,” she said.

But Sierra Club of B.C. campaigner Susan Howatt said the carbon tax is an important step in the right direction that makes B.C. the leader in North America on climate change.

“I’m quite disappointed by the NDP,” she said. “They’re missing some critical environmental legislation here to make political hay.”

She said the NDP’s “Axe the Tax” campaign inaccurately claims big industry is getting a free ride. Big emitters will still be affected by the tax on fuel they use – covering about 70 per cent of what they release. The other 30 per cent are released by industrial processes like the production of cement or aluminum.

“Referring to the carbon tax as simply a ‘gas tax’ is really missing the boat,” Howatt added, noting the carbon tax also applies on natural gas home heat, propane and other fuels.

Howatt said the carbon tax isn’t a silver bullet but a promising part of a suite of options that include cap-and-trade systems, carbon sequestration and improved transit.

“We have to do everything we can to break our addiction to fossil fuels,” she said.

Rather than backing down, Howatt hopes the province ratchets the carbon tax higher yet in the years after 2012, by which time 7.2 cents per litre is to be added to gas prices.

She also said B.C.’s carbon tax has begun to influence federal politicians.

In Ottawa, federal Greens last week unveiled a proposed $50-per-tonne carbon tax that would add 12 cents a litre to gas prices. As in B.C., income taxes would be offset, but the Greens promise more help for rural and low-income people as well as a cap-and-trade system on coal-fired power generators.

Federal Liberal leader Stephane Dion has proposed a carbon tax reaching $40 per tonne after five years that would apply to fossil fuels, but gasoline would be exempt. The “green shift” concept that would redirect the money to low- and middle-income Canadians has been rejected by prime minister Stephen Harper. B.C.’s tax starts at $10 per tonne and climbs to $30 by 2012.