An Alberta economist whose 2016 carbon tax estimates are being cited by Progressive Conservative Leader Blaine Higgs on the campaign trail says the numbers are "obsolete" and no longer accurate.

Trevor Tombe of the University of Calgary contacted CBC News on Wednesday night to say that more recent calculations by his colleague Jennifer Winter — which suggest the PCs are overestimating the cost to consumers — should be used instead.

"Jen's estimates use the best tools available, and mine are obsolete," he said.

Winter, who oversees energy and environment research at the university's school of public policy, published a blog post this week that said PC estimates of a $1,200-per-year cost impact of the Liberal carbon tax are more than double her own calculation.

Her figure is $525 per year.

A math mistake

Progressive Conservative Leader Blaine Higgs has said any money that comes in from a carbon tax will go 'right back out into people’s pockets.' (Catherine Harrop/CBC)

"To me that means they made a math error … or they used inflated assumptions about driving habits or average vehicle fuel efficiency," she wrote.

She said to come up with $1,200, the average household emissions in New Brunswick would have to be 24 tonnes of carbon dioxide a year, taxed at the federal requirement of $50 per tonne.

But she said data on household energy use from 2015 suggest the average household emits 10.5 tonnes — less than half. That produces her figure of $525.

PC Leader Blaine Higgs said he got the figures from a 2016 article by Tombe in Maclean's magazine. It estimated direct carbon-tax costs in New Brunswick at $750 and indirect costs at $500.

Figures out of date

The PCs say an eventual 12-cent-per-litre carbon tax at the gas pumps will not only cost more there but will also have spinoff effects that will ripple through the economy. (Jonathan Hayward/Canadian Press)

But Tombe said Wednesday those figures are now out of date.

"My estimates in the Maclean's piece are superseded by Jen's," he wrote in a message. "I produced the Maclean's piece long before her estimates, and (importantly) before good indirect cost estimates were made possible by Statistics Canada tax policy software."

The $1,200 figure in Tombe's initial article is based on a $50 per tonne carbon tax, the level that would be reached in the fifth year of the federal climate plan.

The PC party is using it based on the widespread assumption that the federal government will impose its carbon price on New Brunswick effective Jan. 1.

The Gallant Liberal government's carbon tax plan shifts a portion of the existing 15.5-cent-per-litre gas tax to a climate fund. This year it's shifting 2.3 cents. By 2022-23 it would reach 11.6 cents a litre, with no net increase in cost to the consumer.

But that plan is likely to violate the federal climate plan, which requires a net increase on the price of carbon emissions. It also says the tax must apply to home heating fuels, which are exempt under Premier Brian Gallant's plan.

If Ottawa confirms the Gallant plan doesn't measure up, it will impose its own price on the province, with a promise to return the revenue either to the government or to consumers in the form of rebates.

Higgs has promised to use any money turned over to the province to issue his own rebates or tax cuts, so that the impact on New Brunswickers is neutral.

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