There is a second fraud lawsuit in the United States against ExxonMobil involving Alberta's oilsands.

The lawsuit, filed on Thursday by the state of Massachusetts, accuses the oil multinational of misleading investors about what climate change measures could cost its operations -- especially those in the oilsands.

"ExxonMobil's misrepresentations falsely justified to investors its riskiest long-term investments, including Canadian bitumen oilsands projects," says the state's complaint, which has not been tested in court.

A similar action by New York's attorney general went to trial this week.

An Exxon lawyer, calling them "bizarre and twisted," has denied the accusations in that case. He said the allegations fail to take into account all the ways Exxon priced carbon risk into its decisions.

As in the New York case, Massachusetts alleges that Exxon told investors it evaluated its projects with a high and increasing price on carbon when it used a much lower figure that remained stable.

It points to extensive public documents and speeches by company executives assuring investors that projects were assessed with a carbon price as high as $80 a tonne.

It cites internal company directives suggesting the price that Exxon actually used was no more than $40 a tonne.

The lawsuit alleges the misrepresentation was even bigger for the oilsands, where Exxon is a major player through its Canadian subsidiary Imperial Oil.

Imperial has declined comment on the fraud cases and referred questions to its parent company.

The lawsuit quotes internal documents referring to an "alternate methodology." It alleges the company would evaluate risk based on legislation that was in place at the time.

"For certain Canadian oilsands projects ... ExxonMobil assumed ... that existing climate legislation would remain in place, unchanged, indefinitely into the future."

Alberta rules in place in 2015 were based on emissions intensity and have been calculated to have imposed a cost of $15 a tonne on carbon emissions.

"ExxonMobil applied these flat, lower proxy costs to both investment decisions at Canadian oilsands projects and reserves assessments," the lawsuit claims.

"For the purposes of evaluating company reserves, ExxonMobil assumed that no new costs would be imposed in Alberta and that only 20 per cent of emissions would be taxed, indefinitely into the future."

The "alternate methodology" had the effect of reducing apparent carbon costs at Imperial's Kearl oilsands mine by 94 per cent, the lawsuit alleges.

The lawsuit also quotes internal documents in which Imperial Oil employees pointed out that actually using the carbon price the company said it was using would result in large writedowns of oilsands assets.

The lawsuit also accuses Exxon of deceiving the public.

"ExxonMobil claims that it is 'working to decrease our annual carbon footprint,' while in fact the company continues its unabated, business-as-usual rapid exploration, development and production of fossil fuel reserves, including its most carbon-intensive reserves, such as those in the Canadian oilsands."

This report by The Canadian Press was first published Oct. 25, 2019.