The New Democrats are calling on the government to refer the party's ongoing dispute with the House of Commons' Board of Internal Economy to the Supreme Court of Canada.

On Friday, lawyers acting on behalf of NDP MPs sent a letter to Justice Minister Peter MacKay requesting he seek cabinet approval to ask the high court to rule on whether decisions by the board are subject to judicial review.

Sixty-eight NDP MPs are on the hook to reimburse more than $2.7 million in parliamentary expenses related to so-called satellite offices deemed improper by the secretive all-party committee.

"This matter is of importance to all Canadians," notes the letter, which is signed by lawyers James Duggan and Julius Grey.

"An early and efficient determination of this issue in a final judgment would not only be in the best interests of the parties and justice but also in our opinion in the interest of all Canadians."

The letter notes the federal government has the power to ask the Supreme Court to weigh in on issues related to the interpretation of the Constitution Acts, as well as the powers of Parliament.

"Your prompt attention to our request is appreciated," the letter concludes.

NDP MPs won't pay until court rules

In a separate letter sent to interim board secretary Marc Bosc, Duggan and Grey say they have advised their clients "not to pay the amounts demanded … unless and until a final judgment has been rendered requiring them to do so."

They also claim the calculations behind the formal repayment requests, which were sent to MPs earlier this month, "contain several errors that are so gross they deserve special mention," including salaries for staff covering time periods before or after they were transferred to a satellite office, and, in some case, when no satellite offices were in operation at all.

"In our opinion, such gross errors are an especially egregious result of 'determinations' made in violation of the rules of natural justice and fairness," the letter notes.

"Our clients were not given a fair hearing, and the 'determinations' were made in their absence in an arbitrary and unreasonable manner, motivated solely by partisan interests in an in-camera process."

In those circumstances, the lawyers conclude, "it would appear that these contested 'determinations' were a foregone conclusion."

The move comes just weeks after the board sent out formal repayment demands instructing the NDP MPs to pay back their share of the cost of the offices, or risk having their own budgets or wages garnisheed.

In a press release announcing the latest move, NDP Quebec caucus chair Robert Aubin said referring the matter to the Supreme Court will prove that MacKay "is committed to our democratic institutions and to saving thousands of taxpayer dollars and wasted time."

The NDP has also filed an application for federal judicial review seeking to have the board ruling declared null and void on the grounds that it is "unreasonable, arbitrary and incorrect," as well as contrary to the rule of law.

The party has also been fighting a board order to repay $1.7 million related to inappropriate mailings.

In a written statement issued on Saturday morning, Government Whip John Duncan dismissed the move as a "stunt."

"The NDP (...) will do anything to avoid paying back the $2.7 million they owe for misusing taxpayer dollars," he said.

He called on the party to "show some respect for the taxpayers of Canada" and immediately repay the money related to the satellite offices and the mail-outs.