Manitoba's NDP government is being accused of "manipulating" a Conference Board of Canada economic report to justify raising the provincial sales tax last year.

The opposition Progressive Conservatives say they've obtained a copy of the contract for the government-commissioned report, which analyzed the NDP's five-year infrastructure plan.

Tory Leader Brian Pallister said the contract states that the report's content had to be satisfactory to the government and could be withheld at the government's prerogative.

"This is clearly a political attempt by the government to manipulate a research institute and create the false impression that somebody out there actually believes what they are purporting to be the truth," Pallister said Monday.

Pallister said the NDP should have instead conducted a study of the economic impacts of not raising the PST. The tax went up from seven to eight per cent last year.

"Manitobans are hurting in their homes and their businesses, they're hurting as a consequence of the government's decisions to jack up taxes," he said.

The NDP says it's standing by the Conference Board of Canada numbers.

"Brian Pallister disagrees with the number of good jobs that will be created through our infrastructure investments because his promise to cut infrastructure funding is not popular with Manitobans," a cabinet spokesperson said in an email.

"He can attack the integrity of the Conference Board of Canada and disagree with the number of jobs our plan will create, but their reputation and business depend on the accuracy of their independent analysis. They stand by the numbers and so do we."

Last week, the Court of Queen's Bench heard a lawsuit that the PCs filed against the NDP regarding the PST increase.