The issue of whether to expel Del Mastro, as well as the fate of his pension, would be sent to a Commons committee for further study. Debate on the matter stretched on for three hours Tuesday, and will resume later this week.
Del Mastro, a former parliamentary secretary to Prime Minister Stephen Harper, was convicted last week of exceeding spending limits during the 2008 election, failing to report a personal contribution of $21,000 to his own campaign and knowingly submitting a falsified document.
The Peterborough MP was booted from the Conservative caucus on the day he was charged in September 2013, and currently sits as an Independent.
"There is no doubt this is a serious violation of the Elections Act and should be treated seriously," said NDP House leader Peter Julian.
The Liberals pushed for immediate expulsion, but other MPs argued that went too far since Del Mastro has said he plans to ask a judge to reopen his defence to allow new evidence to be introduced.
"A decision on expulsion should await such time as the legal avenues available to the member are exhausted," said Conservative House leader Peter Van Loan, noting Del Mastro would have a chance to address the Commons committee.
Del Mastro was not in the Commons on Tuesday. His wife gave birth to their first child, a girl, on Sunday. Del Mastro stands to lose an annual salary of $163,700 if he is suspended. Sentencing is scheduled for Nov. 21.
The Canada Elections Act states that those convicted of an illegal offence cannot sit as an MP for five years. But Speaker Andrew Scheer has noted only members of Parliament can decide on the fate of fellow members.
Last year, the Senate voted to suspend former Conservative senators Patrick Brazeau, Mike Duffy and Pamela Wallin over alleged irregularities in their living and travel expenses.
None was facing charges at the time, although Brazeau has since been charged with fraud and breach of trust. Duffy faces 31 charges, including fraud, breach of trust and bribery. Wallin has not been charged.
In the history of the Commons, there have been only four other cases of expulsion — two of them involving Manitoba MP and Metis leader Louis Riel.
The opposition has sought to frame the Del Mastro conviction as part of a pattern of Conservative indifference towards electoral laws. They point to the so-called "in-and-out" scandal, settled out of court in 2012, in which several Conservative officials were charged in connection with a scheme that allegedly helped the party exceed spending limits.
Former Conservative Peter Penashue resigned his seat last year over ineligible campaign donations, and was defeated in the ensuing byelection in 2013.
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