OTTAWA -- The stunning oversight that allowed a man convicted of attempted murder to be invited to a party in New Delhi with Prime Minister Justin Trudeau is rocking Canada's ties with India just as the government is trying to boost trade in Asia.

The fiasco has left relations between the two countries at an all-time low, said one former Liberal cabinet minister, while other observers call it proof the government must jettison the photo ops in traditional Indian clothing in favour of a more serious foreign policy stance.

Ujjal Dosanjh, a former Liberal health minister, ex-premier of British Columbia and one-time provincial attorney general, accused his old federal party of being too close to Sikh separatists even before Trudeau's arrival Sunday in India.

Inviting Jaspal Atwal to a reception, however, was the last straw, Dosanjh suggested.

Atwal was convicted of attempting to kill Indian cabinet minister Malkiat Singh Sidhu on Vancouver Island in 1986. He was also charged, but not convicted, in connection with a 1985 attack on Dosanjh, a staunch opponent of the Sikh separatist movement's push for an independent state of Khalistan.

"Mr. Trudeau can perhaps salvage our relationship (with India), but I think it hit rock bottom with this," Dosanjh said in an interview Thursday.

"It was already sliding downwards from the moment they got to India."

Trudeau's office said the invitation was a mistake and was rescinded as soon as Atwal was discovered on the guest list. However, he showed up at a reception earlier in the week in Mumbai and was photographed with Sophie Gregoire Trudeau, the prime minister's wife.

Dosanjh said he couldn't believe what he was seeing when he saw the photograph.

"I don't particularly want the man punished again, but it was disbelief that he would be able to associate with a reception in Mumbai," said Dosanjh.

"How could the RCMP, how could the PMO, how could the high commissioner -- how could all three of them -- be blind to this?"

Atwal was added to the guest list by British Columbia MP Randeep Sarai, one of 14 MPs in India with Trudeau. Sarai has acknowledged he should have used better judgment.

In a statement, Sarai said he takes full responsibility for his actions.

"I apologize without reservation for my role in this situation, which has become an unfortunate distraction from the work, achievements, objectives of the prime minister and his team during this historic trip to India," he said.

"Let me be clear -- this person should never have been invited in the first place. I alone facilitated his request to attend this important event."

David Hyde, a Toronto-based security and risk management specialist, said either the RCMP dropped the ball in properly vetting the guest list, or they were given a false name that didn't raise a flag.

"To me, it's pretty unconscionable that it would happen," Hyde said.

The incident is embarrassing for the prime minister, said Chris Mathers, a security consultant who helped protect 24 Sussex Drive as a young Mountie when Trudeau's father held office.

But Sarai didn't help matters by independently inviting Atwal to the reception.

"If the members of Parliament themselves are working at cross-purposes to the security services, how are we supposed to prevent stuff like this?"

The incident raises questions about the ability of Trudeau's office to plan and execute a foreign trip, said David Mulroney, a career public servant who served as a foreign policy adviser to former prime minister Stephen Harper.

"We shouldn't be sending the prime minister into situations that are uncertain and where the visit is consumed by the drama of whether something that should have been predictable happens or not. That's happening too much."

Mulroney, a former Canadian ambassador to China, recalled Trudeau's December trip to the People's Republic, where he faced criticism for being unable to announce the start of formal free trade talks.

All of it is a symptom of something more serious: a failure to think seriously about our interests in the world, said Mulroney.

"We're relying too much on how photogenic and how popular we think the prime minister is, and it's beginning to backfire on us."

Trudeau's turbulent trip to India has drawn criticism from the Conservatives and raised eyebrows internationally.

Trudeau had to profess his support for a united India after meeting with the chief minister of Punjab, who had accused the prime minister of appointing Sikh separatists to his cabinet. And some critics insist Trudeau is being snubbed by Indian Prime Minister Narendra Modi, even though the two are to meet on Friday.

Modi tweeted Thursday that he is looking forward to meeting Trudeau and that he appreciated "his deep commitment to ties between our two countries."

But his decision to wait five days to meet Trudeau is a deliberate demonstration of his displeasure over Canada's handling of the Sikh issue, Mulroney said.

"It is a real signal that all is not well and he doesn't appreciate what he's hearing about our position," he said. "He's got a strong personality and he's not afraid of sending strong messages."

However, Trudeau got some back-up Thursday from NDP Leader Jagmeet Singh.

Singh -- who has faced criticism for failing to unambiguously denounce Canadian Sikhs who glorify the mastermind of the Air India bombing -- said Indian complaints about Canada or its politicians shouldn't be taken as gospel.

"I reject the baseless attacks against Canadian cabinet ministers and we should be wary of any international interference in our political affairs, especially when it's targeted at minorities such as members of the Sikh community," Singh said in a statement.

"The Indian government has a troubling record of conflating human rights advocacy with extremism for their own political benefit. Like all Canadians, I condemn all acts of terrorism and violence while maintaining a fundamental belief in the freedom of belief and expression."

As for Atwal, Singh said: "There are a lot of questions here including how this individual was granted admission into India after being convicted of shooting a member of the Indian government while at the same time many, including myself, have been barred entry into India for speaking out about human rights."