In a frank exchange with CTV, the Russian ambassador to Canada said we may never know the details of a spy operation his country is accused of participating in in Canada, since he has made a deal with Ottawa to keep quiet about the case.

CTV's Ottawa Bureau Chief Robert Fife reported the story on Thursday after attending a cocktail reception at the Russian embassy and chatting candidly with the ambassador.

Sub-Lt. Jeffrey Delisle, a naval intelligence officer, is in custody on charges of passing secret military information to a foreign entity. CTV has reported Delisle passed on secrets to the Russians and Canada retaliated by expelling several Russian diplomats.

Russian Ambassador Georgiy Mamedov told Fife he couldn't speak about the case, but then continued talking.

"I said tell me more, and he said 'I can't tell you more because we have a deal with the Canadian government to keep everything confidential perhaps until this court case is over,'" Fife told CTV's Canada AM.

Fife then asked Mamedov about Delisle, and whether he was a spy working for the embassy.

"He said 'I don't know that because I'm not in charge of human intelligence at the embassy.' In other words the spy operators who work out of the embassy don't necessarily work for him."

Mamedov went on to tell Fife it is important for Moscow to have "good relations" with Canada and suggested the story is being kept quiet in order to preserve that relationship.

Asked directly if Delisle was spying for the Russians, Mamedov said: "I don't know because I am not the guy who controls Humint (human intelligence). But I can tell you what you said about some people in my embassy are dead wrong."

CTV reported that six Russian diplomats have left Canada since Delisle was arrested in mid-January, including two military attachés. Sources say some of those diplomats were asked to leave as a result of the spy scandal.

Mamedov declined to say which of the six Russians were asked to leave by the Canadian government.

"I am not at liberty to discuss because I don't want to influence your judicial process," he said.

Mamedov also said it is possible Russia's role in the Delisle spying case will never be known.

"It will depend on the entire interests of our bilateral relations because you are interested in good relations with the Russians . . . so I am working for you as much as for my taxpayers."

The ambassador, who has been in Canada since 2004, would not say if Moscow asked any Canadian diplomats to leave.

Insiders say Canada is downplaying Russia's involvement in the spy affair to avoid tit-for-tat expulsions of Canadian diplomats in Moscow.

According to court documents, investigators allege that between July 6, 2007 and Jan. 13, 2011, Delisle committed a breach of trust and communicated to "a foreign entity information that the Government of Canada is taking measures to safeguard."

The Russians allegedly recruited Delisle while he was working as a naval intelligence officer in Ottawa. He ended up in Halifax where sources say he handled highly sensitive information.

Exactly what secrets Delisle allegedly passed on to the Russians is not known.

Military attache Colonel Sergey Zhukov, deputy military attache Lt.-Col Dimitry Fedeorchatenko; diplomats Konstantin Kolpakov and Dimitry Gerasimov; and technical staffers Mikhail Nikiforov and Tatiana Steklova were removed from the Foreign Affairs list of Russian diplomats over the past month.

With a report from CTV's Ottawa Bureau Chief Robert Fife