NDP leadership hopeful John Horgan said today he will expand the carbon tax if he becomes premier, and admitted his party botched the issue in the last election.

Horgan said he would widen the scope of the carbon tax to include big industrial emitters -which, under the current structure, he said have an out that is effectively a tax writeoff -and review how the tax is applied and its revenues spent under a new Fair Tax Commission.

Expanding the carbon tax flies in the face of the NDP's 2009 election platform, which called on the B.C. Liberal government to scrap the tax entirely. Horgan admitted he supported that position at the time as opposition energy critic.

"We misread the public mood on the carbon tax," he said. "We collectively made a mistake in the 2009 election by opposing the carbon tax."

Horgan, MLA for Juan de Fuca, outlined his environmental platform Wednesday, which includes: A moratorium on new run-of-river power projects; an independent review of all private power projects and capital spending by BC Hydro; support for West Shore light rail; improved energy conservation projects; a new subsidiary of BC Hydro to focus on small and medium sized publicowned green power projects; an endangered species act; protection for old-growth forests; a budget boost for B.C. parks; and a move away from open net pen salmon farms to closed tank systems.

He said he wouldn't rule out future tax increases to help pay for environmental programs.

"I feel strongly that we need a solid foundation to go into the 21st century," said Horgan.

"We have fallen behind other jurisdictions. We were world leaders."

The B.C. government introduced the carbon tax in 2008 at a rate of $10 per tonne of associated carbon, or carbonequivalent, emissions. It's the first of its kind in North American and applies to virtually all fossil fuels, with a plan to increase it to $30 a tonne by 2012.

Liberal leadership candidates have wrestled with what to do after 2012. George Abbott proposed a referendum, while Kevin Falcon expressed concern no one has followed B.C.'s lead. Christy Clark said Wednesday she supports the tax and opposes the referendum.

Horgan said he's one of the only leadership candidates from either party to unveil an environmental platform.

The NDP votes on a new leader April 17.