Finance Minister Bill Morneau did not seek clearance from the federal ethics commissioner before he introduced pension-reform legislation that could benefit the firm founded by his father and in which he still owned one million shares.

The minister's office says he did not need to seek permission – and that an "ethical screen" was in place to ensure he did not run afoul of conflict-of-interest rules, but NDP ethics critic Nathan Cullen said "alarm bells" should have been going off in his office.

Mary Dawson, Ottawa's ethics watchdog, is officially examining whether Mr. Morneau contravened Canada's ethics laws when he tabled a bill to rewrite federal pension laws that could benefit Morneau Shepell, one of four major firms in the human-resources and pension-management sector in Canada.

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Read more: Morneau issue flagged for ethics czar weeks before she launched probe

News of her investigation broke on Nov. 10, just before the Commons went on a one-week break.

The opposition parties had fresh ammunition for Monday's attacks after The Globe and Mail revealed that retired postal workers had warned Ms. Dawson in a letter on Sept. 18 that the Finance Minister could be in a conflict of interest over the pension legislation, Bill C-27, and its potential benefits for Morneau Shepell. The same letter was delivered to Mr. Morneau's office on Sept. 18.

"Bill C-27 is not only a clear attack on workers' pensions, it is also a massive conflict of interest," Mr. Cullen told the House.

Mr. Morneau repeatedly declined to answer when MPs asked him whether he had sought the approval of Ms. Dawson before sponsoring Bill C-27.

Instead, he tried to put the matter behind him and announced that he had now sold all his shares in Morneau Sheppel and donated to a charity the $5-million in profits he earned since becoming Finance Minister.

"The minister just said that now that he has sold all of his shares in Morneau Shepell, he can now 'work on behalf of Canadians.' What does that say about the last two years while he held those shares?" Conservative finance critic Pierre Poilievre shot back. "During that time, he introduced a bill creating the very targeted-benefit pension plans that his company designs and profits from."

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Asked whether Mr. Morneau had any discussions with the federal ethics commissioner before tabling Bill C-27, Ms. Dawson's office declined to comment, citing the investigation into the minister and privacy rules.

"The office cannot divulge anything that Minister Morneau may have raised with [her], as all communications between the commissioner and individual public office holders are confidential," spokeswoman Margot Booth said.

Mr. Morneau's communications director, Dan Lauzon, told The Globe that the Liberal government believes there was no conflict of interest and no requirement to run Bill C-27 past the ethics commissioner. "All appropriate screens were in place from Day One, and we believe no conflict exists. … We will continue to work with the ethics commissioner and she can count on our full co-operation, as she has from the very beginning."

In the House of Commons, Prime Minister Justin Trudeau tried to defend his beleaguered Finance Minister, accusing the opposition of "cheap shots" and "mudslinging."

Mr. Cullen said Mr. Morneau has shown "an ethical blindness" and should have alerted the ethics commissioner as soon as he decided to rewrite federal pension law.

"Smart people might think that [it is prudent to clear] an action or bill prior to it being introduced when conflict-of-interest alarm bells should be going off," Mr. Cullen said.

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When Mr. Morneau introduced C-27 in October of 2016, it was widely believed he had placed his assets – including shares in Morneau Shepell – in a blind trust.

However, as The Globe first reported last month, Mr. Morneau did not set up a blind trust or divest his assets.

Bill C-27 would allow Crown corporations and federally regulated companies the option of setting up target-benefit pension plans for their employees instead of defined-benefit plans.

When he was executive chair of Morneau Shepell, Mr. Morneau publicly advocated for target-benefit plans, which the opposition parties and unions say shifts the risk to employees.