Prime Minister Justin Trudeau is standing by a senior government official who floated the theory that rogue political factions in India orchestrated the embarrassing invitation of a would-be political assassin to a formal dinner to make the Canadian government appear sympathetic to Sikh extremism.

The Opposition hit Trudeau hard during question period Tuesday — the prime minister's first since his India trip — over how Jaspal Atwal was invited to two receptions in India.

Atwal was a member of an illegal Sikh separatist group and was convicted of attempting to assassinate Indian cabinet minister Malkiat Singh Sidhu in 1986. He was also charged — but not convicted — in the 1985 attack on Ujjal Dosanjh, who later became B.C. premier and a federal Liberal cabinet minister.

In a background briefing arranged by the Prime Minister's Office, a senior government official with knowledge of the prime minister's security protocols suggested to reporters that the invitation fiasco was arranged by factions within the Indian government.

Prime Minister Justin Trudeau answers a question from Opposition Leader Andrew Scheer about Jaspal Atwal's alleged connections with Indian state intelligence 0:54

The Conservatives identified the official as Trudeau's national security adviser, Daniel Jean, and pressured Trudeau to say whether he agrees with Jean's "conspiracy theory." "A senior security official made these allegations. Does the prime minister agree or disavow those allegations?" asked When one of our top diplomats and security officials says something to Canadians it's because they know it to be true. - Prime Minister Justin Trudeau Opposition Leader Andrew Scheer. Trudeau used his response time to accuse the previous Conservative government of using the public service for political means. "Our professional, non-partisan public service does high quality work and when one of our top diplomats and security officials says something to Canadians, it's because they know it to be true," Trudeau responded. Trudeau meeting with MP Tuesday Atwal attended at least one event tied to the Trudeau visit at which he was photographed with Sophie Trudeau and Minister of Infrastructure and Communities Amarjeet Sohi.

Atwal received his invitation through B.C. Liberal MP Randeep Sarai, who put the former member of a banned extremist group on the guest list for a dinner at the Canadian High Commission in India.

Sophie Trudeau and Jaspal Atwal are pictured together in Mumbai on Feb. 20. (Name withheld by request)

He also was invited to dine with the prime minister at a formal event hosted by the Canadian High Commissioner Thursday in Delhi, but that invitation was later rescinded.

Trudeau said he would meet with Sarai Tuesday.

The Surrey member of Parliament, one of 14 MPs who travelled with Trudeau, sent out a statement last week taking the blame.

"Let me be clear — this person should never have been invited in the first place," he said.

"I alone facilitated his request to attend this important event. I should have exercised better judgment, and I take full responsibility for my actions."