Tyrone Benskin has been stripped of his role as official-languages critic until he pays the $58,000 he owes to the Quebec revenue agency.
The provincial agency has contacted the House of Commons to seize part of his $160,000 MP's salary because of outstanding tax debts from 2007 to 2011.
The Montreal MP had been an actor in films, including the popular "300," before being elected in 2011.
Benskin has apologized in a statement.
"In order for our society to be prosperous and fair, each citizen must do their part. I haven't always done mine and I apologize," he said.
"Fortunately, I am working on sorting out my situation with the Canada Revenue Agency. I intend to pay back every last cent of the money I owe, as soon as possible."
He also offered an explanation about why he was so late.
"The life of an artist isn't always easy. I have had lean periods," he said. "I have lived in precarious conditions, not knowing what the future had in store for me, sometimes without a contract for several weeks, or even months. I have had to juggle bills.
"My situation has prevented me from fulfilling all of my tax obligations and I am truly sorry. I recognize that it is my responsibility and I will fulfill it directly and personally."
NDP Leader Tom Mulcair says he's happy the MP apologized — but will now be sidelined until he settles up with the taxman.
"He has to pay his taxes, like everyone. He will do it. He will do it completely. He apologized — which was the right thing to do," Mulcair told reporters Friday in Trois-Rivieres, Que.
"Until then, I have removed him from our shadow cabinet. So he loses his responsibility in official languages until he pays his taxes."
The NDP has come under some criticism for the vetting of candidates in the 2011 election, where in a swift and surprising breakthrough it elected 59 MPs in Quebec.
In the days following the election, the CVs of some of the rookie MPs came under intense scrutiny in Quebec media and from the Bloc Quebecois — which had been nearly wiped out by the so-called Orange Crush.
Since being elected, Benskin had fought for tax changes in cases like his.
He presented a private member's bill, C-427, which was rejected by the governing Tories. It would have averaged out certain people's earnings over a period of years, so the tax hit would not suddenly spike in an occasionally prosperous one.
He described the bill last year as an attempt to help independent artists who can't access Employment Insurance and struggle with a "feast or famine" cycle.
"This is a deeply personal project for Mr. Benskin, who has been an artist for over 30 years," he said in a statement last year.
"C-427 is born of an intimate understanding of the numerous and pressing challenges faced by contemporary Canadian artists."
The governing Conservatives used the Benskin example to paint the NDP as hypocrites.
They said that while flinging various accusations about abuse of the public purse, and also about being lax on tax evasion, the NDP should look to its own benches.
A pair of government ministers brought up the Benskin issue Friday. Industry Minister Christian Paradis was asked about the Senate expenses scandal and answered about Benskin.
He said Mulcair hasn't disciplined his MP enough.
"When the NDP wants to preach by example I think their own members should be compliant with the tax law... They should be thrown out of the caucus in the meantime," Paradis said in Ottawa.
"They have to solve their issues. This is very serious."
-With files by Alexander Panetta
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