You cannot get any closer to power in Canada than standing beside the prime minister's desk.

That is where an accused Russian spy was during the recent bilateral meeting between Justin Trudeau and Ukraine Prime Minister Volodymyr Groysman.

Stanislav Yezhov, a key aide and interpreter for Groysman, found himself in a different place Wednesday night.

He was arrested by his country's state security service and accused of treason.

He was in the room for a number of high-level meetings in Ottawa, including private sessions with Trudeau and Gov. Gen. Julie Payette.

He also interpreted an interview Groysman conducted with CBC News as part of his official visit, which included testimony before the House of Commons foreign affairs committee.

Foreign Affairs Minister Chrystia Freeland, who is of Ukrainian heritage, was in Kyiv on Thursday as the scandal unfolded.

Her staff said she was unavailable to comment.

Given the timing of the visit on Oct. 31, the case raises serious questions for the Canadian and Ukrainian governments, said a security and intelligence expert.

"Him standing behind the prime minister's desk is a little worrisome, depending on what was on his desk at the time," said Phil Gurski, a retired CSIS officer. "At this point, the major concern that I would have is — what was spoken? What was said on a bilateral basis between Canada and Ukraine that is now in the hands of the Russians?"

Arms sales, G7 discussed

​Groysman, in his interview with CBC News that day, said the two countries discussed the issue of adding Ukraine to the list of countries where Canadian arms manufacturers can sell weapons and about Trudeau using the upcoming chairmanship of the G7 to focus attention on the war-torn eastern European country.

A spokesman for Trudeau offered little comment, beyond confirming that Yezhov was part of the Ukrainian delegation.

Cameron Ahmad said Canada had its own interpreter in the room.

The Security Service of Ukraine (SBU) said Thursday it had opened a treason case, but not yet laid charges against the interpreter, who was allegedly recruited by Russia's Federal Security Service (FSB)

A statement by the SBU accused Yezhov of collecting "data on the activities of governmental institutions by means of special equipment."

He allegedly passed information to his Russian contacts "through electronic communication channels."

The agency's statement also suggested Yezhov had been under surveillance for a while but was allowed to go about his business as security officers gathered evidence.

Yezhov, right, provided translation for a CBC News interview with Groysman, left, during his October visit to Ottawa. (CBC)

That raises the possibility the Ukrainian security service knew about the potential security risk during Groysman's visit to Ottawa.

Gurski said that is significant and something Canadian officials, particularly Freeland, should follow up on immediately.

"What the Ukrainians should have done is not permitted him to travel with the prime minister to Canada for bilateral talks," he said.

"They had reasonable grounds to suspect he was spying for the Russians, he has no business to be part of that delegation."

Gurski was not prepared to call it a security lapse, but believes a review should take place.

"I would say that if it's not a security lapse we need to revisit the protocols that we function under when it comes to visiting delegations," he said.

Inner circle

​Yezhov, who has long been part of Groysman's inner circle, also took part in meetings with British Prime Minister Theresa May last July and former U.S. vice-president Joe Biden in 2016, according to published reports in Britain.

SkyNews quoted May on Thursday as saying she was aware of reports that Yezhov had been arrested but deferred to Ukrainian authorities.

The Ukrainian embassy in Ottawa confirmed that "a member of staff" working for "cabinet ministers" was detained Wednesday by the SBU under suspicion of illegally collecting information in favour of the Russian Federation.

"He is suspected in a state treason. The investigation is underway. The decision on the case will be ruled by the Ukrainian court," said the statement.