The letters or flyers MPs mail for free to residents of their own or other ridings should probably be banned, according to Duff Conacher of Democracy Watch, a democratic reform advocacy group.

Failing an outright ban, the material should at least be vetted by the auditor general, Conacher said.

This week, the federal NDP was asked to repay $36,000 to the government because 23 of its MPs sent almost two million pieces of mail last year to several ridings, including some facing imminent byelections.

As well, the NDP has been asked to reimburse Canada Post for the cost of the postage, estimated to be worth $1.13 million, for a total of $1.17 million.   

The request was issued by the secretive Board of Internal Economy (BOIE), a committee composed of four Conservative MPs, two NDP MPs and one Liberal MP. The powerful closed-door committee regulates the expenditures of all MPs.

In its decision the board said the NDP used parliamentary resources for partisan purposes.

NDP says it followed the rules

The NDP insists it has followed the rules. It stated it intends to go to court to challenge the board's request to repay.

It's not unusual for MPs to send mailouts to ridings other than their own, often for the purpose of making partisan attacks. But the rules stipulate the content must not advance the electoral chances of a political party, nor should it fundraise or attempt to recruit new members to the MP's political party.

Although the NDP mailings in question may breach the rules, Conacher considers almost all MPs' mailouts a form of advertising.

In an interview, he pointed out the auditor general of Ontario has the power to vet all provincial government taxpayer-funded ads to determine if they're partisan. "The AG can say, 'No, this ad is promoting the government party, not informing people about a new program or a new law,'" he said.

Part of every MP's office budget allows for free envelopes as well as "franking," meaning that by affixing their signatures to an addressed piece of mail, MPs can have letters delivered postage-free anywhere in the country.

Often the mailouts are just newsletters that include photos of the incumbent MP at community events, or relate his or her position on bills before the House of Commons.

"Always the local MP is highlighted," Conacher said. "It's sort of free advertising for the next election if they're going to run," he said.

Mailouts are often partisan attacks

Often, mailouts by MPs are sent into other ridings to attack an opposing party. The board doesn't penalize that behaviour.

On CBC News Network's Power & Politics, Gerald Kaplan, a panel member on the program, showed host Evan Solomon a flyer he received a few years ago from Alberta Conservative MP LaVar Payne.

The flyer, stamped "no postage required" began, "When it comes to fighting anti-Semitism, the Conservative government will not compromise."

"Which, of course, means that the others will compromise," said Kaplan, reached by phone from his home in Richmond Hill, Ont.

Kaplan wonders how an MP from Medicine Hat, Alta., got his name and address. He suspects he was targeted because he is Jewish.

The NDP's 2013 mailouts directed recipients to NDP.ca, where donations are solicited. The letters also invited people to choose who is the best federal leader, with NDP Leader Tom Mulcair's name placed first among a choice of four leaders.

"I think the NDP made a mistake," Conacher said, but added the difference was of "degree." He continued, "To say that these have to be paid back in full when the others weren't is the ruling of a kangaroo court."

Gregory Thomas of the Canadian Taxpayers Federation said that whether or not the NDP broke the rules, "We object to the use of the postal system."

He pointed out a motion by former Liberal leader Michael Ignatieff in 2010, narrowly passed by the House of Commons, which banned the practice of MPs sending "10 percenters" or political flyers to other ridings.

"Then they [MPs] exploited a loophole that allows you to send letters," Thomas said.

'Partisan witch hunt'

The NDP has called the Board of Internal Economy a "kangaroo court" conducting "a partisan witch hunt."

On that point, Conacher agrees. "It is a kangaroo court by definition because it's politicians judging politicians from another party."

However, he points out, it's only recently the NDP has complained about the board, although it's been a member of the powerful committee for almost 50 years, ever since it became an official federal party in the '60s.

"For years they [the NDP] co-operated," Conacher said. "And now it's a kangaroo court?"