NDP Leader Tom Mulcair has written to ethics watchdog Mary Dawson asking her to review her earlier decision clearing Defence Minister Harjit Sajjan of violating the Conflict of Interest Act when he refused to hold an inquiry into the treatment of Afghan detainees.

In the letter, Mulcair says Sajjan's recent decision to overstate the importance of his role in Operation Medusa, one of the biggest battles Canadian troops fought during the Afghan war, calls into question the minister's credibility.

"In light of the new information that has come to light, I am urgently requesting that you review your decision," Mulcair wrote.

"These revelations seriously call into question the minister's honesty and forthrightness with respect to his role, and what information he had access to throughout his time in Afghanistan," Mulcair added.

A spokesperson for the Prime Minister's Office said it "won't be commenting" on the letter.

Jordan Owens, a spokesperson for Sajjan, said the minister, too, had nothing new to add. "Last year, after reviewing allegations from former NDP MP Craig Scott, the conflict of interest and ethics commissioner declined to open an investigation, and we consider this matter closed," said Owens.

Former New Democrat MP Craig Scott, who lost his seat in the last election and has since returned to teaching at York University in Toronto, spearheaded an e-petition last spring calling on the Liberal government to hold an inquiry into the treatment of Afghan detainees.

Sajjan, responding on behalf of the government, turned down the plea. At the time, he said the matter had been investigated by the Military Police Complaints Commission and that Canada had obeyed international law.

The 1st ethics decision

That response prompted Scott to write Dawson asking her to investigate whether Sajjan had violated the Conflict of Interest Act.

Scott argued that because Sajjan acted as a liaison officer between the Afghan National Police and the Combined Task Force, Sajjan would likely have been called to testify and was therefore in a conflict of interest when he declined to hold the inquiry.

Dawson did not launch an investigation, but she did speak with Sajjan and said she was satisfied the defence minister had no knowledge of alleged Afghan detainee abuse.

NDP leader Tom Mulcair asks whether Defence Minister Harjit Sajjan's claims about his military career have an impact on his role in the Afghan detainee issue 1:06

Mulcair's letter said Sajjan's recent comments claiming to be the "architect" of Operation Medusa, and subsequent retraction and apology when those statements were challenged, suggests that the minister's credibility cannot be trusted at face value.

"This information casts further doubt on the minister's truthfulness in the account of his role that he provided to you," he wrote.

Mulcair further states that since Sajjan did have a significant role in Canada's deployment to Afghanistan it is "simply not plausible" that he did not know what was going on with Afghan detainees.

Under pressure

Sajjan meanwhile has bowed out of an annual fundraising event originally set up for veterans of the war in Afghanistan, an event whose main beneficiaries include military personnel returning from combat.

Sajjan had been scheduled to speak at the eighth annual "To the 'Stan and Back" event Tuesday, but founder Cheri Elliott said she was told a scheduling conflict had arisen and he would not be able to attend.

"The official reason for his not being able to attend is he was asked to be elsewhere at the time. That is what I was told," said Elliott, who is the mother of a serving Canadian Forces member.

The minister spoke at the same event last year, which raises money for service members as well as first responders dealing with PTSD and other psychological trauma.

The embattled defence minister is, however, pressing ahead with a speech Wednesday to members of the Conference of Defence Associations Institute, billed by his department as an update on "the state of Canadian defence."

Sajjan, a former soldier and veteran of the Afghan war, was back in question period Tuesday, where he again faced multiple calls for his resignation for having exaggerated his role in Operation Medusa.