The House of Commons Board of Internal Economy is broadening its investigation and looking into "remedies" after it found New Democrat MPs broke the rules around mass mailings.

House of Commons Speaker Andrew Scheer on Tuesday confirmed the decision on the mailings.

Canada Post is required by law to provide free mail delivery service to and from MPs so they may communicate with their constituents.

However, owing to past controversies, the House of Commons has established rules around the content of the mail eligible for this service.

In a terse written statement issued on behalf of the board, Scheer said it has determined that "certain mailings" sent out by New Democrat MPs "were prepared by and for the benefit of the NDP as a political party and to advance electoral purposes, and are therefore in contravention of the bylaws."

The board has asked the House to "provide advice on appropriate remedies at its next meeting."

The NDP has also been directed to turn over "all proofs of mailing related to this matter" to House administrators for further analysis.

'Well over a million mailings' under review

Conservative whip John Duncan, who serves as spokesman for the board, told reporters he's not prepared to give an estimate on the total amount that the party could end up owing the House.

"I think some numbers are floating around out there, but I don't want to do any of the prejudging," he said outside the House on Tuesday morning, adding that the board is looking at "well over a million mailings."

The NDP, on the other hand, suggests the entire process was predetermined.

"Today's unprecedented move confirms that under Stephen Harper's banana republic Conservatives, rule of law and due process are secondary to political gamesmanship," said NDP House leader Peter Julian.

Julian said the mailings in question were part of an "outreach" program the NDP undertook last year as part of its role as the Official Opposition.

The issue seems to be that the letters addressed and mailed to individuals in House of Commons envelopes included the web address for the NDP's site, something the rules prohibit.

The NDP, however, has produced at least one similar mailing from other parties that includes a partisan web address as well.

"The Conservatives want the right to be able to carpet bomb my riding with propaganda," charges NDP MP Pat Martin, "but they want a unilateral disarmament — that the NDP isn't supposed to have the same tool in their toolbox."

Duncan insists the process has been "thorough and fair."

"They should be accepting responsibility instead of impugning everyone else, including the Speaker."

Duncan said the NDP may owe Scheer an apology after issuing a statement suggesting the impartiality of the chair was now in question.

"They know darn well he's in no position to defend himself," Duncan said.

If the party refuses to pay the money back, Duncan hinted that the board could take steps to recoup the cost of the mailings.

"MPs receive budgets, and the NDP, as a party, receives a research budget and salaries. There are obviously mechanisms to recover monies."

House committee also looks into NDP spending

Meanwhile, Conservative and Liberal MPs joined forces to pass a motion authorizing the House affairs committee to continue its parallel investigation into NDP spending practices — including both the mass mail drops and the satellite offices — over the vigorous but ultimately unsuccessful objections of the New Democrat minority at the table.

In making the case for his motion, Conservative MP Tom Lukiwski suggested that NDP staffers may have made a "deliberate attempt" to "mislead House officials" on where the staffers at the Montreal office would be working.

He also pointed to what he sees as clear contradictions between claims made by the NDP and statements made by House of Commons officials, including House Clerk Audrey O'Brien.

"Someone is not telling the truth," he said.

He wants the committee to hear from O'Brien before moving on to any other witnesses, which will likely delay the next round of hearings until the fall, as she is on medical leave until July.

Mulcair’s name does not appear in the final version of the motion, but the committee could also attempt to bring him back for a followup appearance, something that his office has said he's unwilling to do.

In the interim, the party has been asked to produce more documentation related to the lease of the Montreal office.

The New Democrats fired back by serving notice of a motion of their own to have the committee look into BOIE policies on paying legal fees for MPs, which, it suggests, can also mean covering expenses related to offences allegedly committed before being elected to Parliament.

The NDP could put the proposal forward for debate when the committee reconvenes on Thursday.