Federal Conservatives are putting a new twist on an old tactic: spying on political opponents.

They're no longer content to send observers to rival parties' public events, passively monitoring proceedings in hopes of spotting a gaffe that can be exploited.

They're now employing agents provocateur who actively try to instigate a miscue, secretly record it and then leak it to the media.

Liberals, who've been on the receiving end of the ploy twice in the past three months, call the tactic entrapment, unethical and "Nixonian."

And they worry it could lead to the end of candour in federal politics, with wary politicians reduced to mouthing platitudes and reciting carefully scripted talking points.

But the Conservatives are making no apologies.

They maintain Canadians have a right to know what Liberal MPs and candidates really think, particularly if their candid views are at odds with those of their leader, Justin Trudeau.

"It's not surprising that Liberals don't want Canadians to know what their true feelings are on important issues," Conservative party spokesman Cory Hann told The Canadian Press.

"What the Liberals are really upset about is that they were caught having one of Trudeau's top advisers deliver anti-Israel messages to certain segments of the Canadian public ... (And) I can see why the Liberals don't want it known that a senior Liberal MP thinks Justin Trudeau is a bozo and in over his head."

Leslie quizzed on Gaza conflict

Hann was referring to retired general Andrew Leslie, a star Liberal recruit who advises Trudeau on foreign policy, and veteran Toronto MP John McKay, both of whom have fallen victim to the Tory sting operation.

Earlier this week, Sun News Network received a recording from a roundtable discussion Leslie hosted last month on veterans' issues, during which a young woman — identified by the Liberals as Alexandra Constantinidis, parliamentary assistant to Conservative MP Rob Anders — asked the would-be Liberal candidate about his views on the Israel-Hamas conflict in Gaza.

In the course of a lengthy response in which he asserted Israel's right to defend itself and to kill members of terrorist organizations such as Hamas, Leslie criticized Israel for "firing indiscriminately" on Palestinian women and children.

According to the Liberals, the Conservatives first offered the recording to the Centre for Israel and Jewish Affairs, which refused to get involved.

The CIJA declined to confirm or deny that assertion but issued a careful statement from CEO Shimon Fogel to The Canadian Press.

"We have met with General Leslie previously. We know the General to be fully appreciative of the security challenges facing Israelis and shares our view as to Israel's responsibility to defend itself and the destructive influence of Hamas," Fogel said.

"His choice of words regarding Israel's tactics was unfortunate and we look forward to meeting with him again to receive re-assurances that his views are consistent with those articulated by Justin Trudeau."

The Conservatives have not been so guarded.

The party sent out a fundraising email blast mid-week, slamming Leslie's "stunning lack of awareness of the dangers Israel faces," asserting that his comments reveal "the Liberals' true position on Israel" and proclaiming that "only the Conservatives' stand on Israel is reasonable and right."

Similar sting operation against Liberal MP John McKay

In a similar sting operation last June, McKay was taken aside by one of three young men who attended a public event in Carleton Place, just west of Ottawa.

The man asked to speak to the Liberal MP confidentially about Trudeau's decision to veto would-be candidates who don't support a woman's right to choose abortion.

McKay, a staunch pro-life advocate, said he initially thought the edict was a "bozo eruption" and went on to suggest Trudeau's advisers have "no political sense whatsoever."

Unbeknownst to McKay, the conversation was being surreptitiously recorded.

A recording of his comments was subsequently given to CTV by someone the broadcaster reported as having "Conservative leanings."

The young man who provoked McKay's outburst appears to be Trevor Stack, founder of the University of Victoria Conservative club who served as an intern in Health Minister Rona Ambrose's office over the summer.

After viewing photos Stack recently posted on social media, including one posing with Prime Minister Stephen Harper, McKay said he's "pretty sure that's the guy."

One of the other young men who accompanied Stack to the event appears to be Allan Mason, who worked as an intern in Justice Minister Peter MacKay's office this summer.

Both Stack and Mason signed in for the event, although Stack spelled his surname as Stacks.

Ambrose's office did not respond to a request for comment on the appropriateness of a minister's intern engaging in such conduct.

'Worrisome trend'

McKay believes the two incidents reveal a "worrisome trend" in federal politics.

"It speaks to an ethical pattern of gotcha politics and gotcha politics is a detriment to our democracy," he said in an interview.

While young Tories may view such sting operations as youthful hijinks, McKay warned their participation in dirty tricks may come back to haunt them later as they pursue professional careers.

Or, he said it could eventually lead them into more serious misconduct a la Michael Sona, the young Conservative who was convicted last month of misdirecting voters to the wrong polling stations in Guelph, Ont., in the 2011 election.

"I suggest to both of these young people (Stack and Constantinidis) that they look to their future when they're doing this stuff because Mr. Harper will not be there to protect you."

For deputy Liberal leader Ralph Goodale, such "covert operations" of the Conservatives "all has a Nixonian kind of feel to it."

"Certainly (it indicates) a lack of moral compass and, as Mr. Nixon amply demonstrated, when that is the modus operandi of your government, it's not going to end well," he said, referring to disgraced former U.S. President Richard Nixon.

Goodale said the tactic is designed to "impose a chill" on candid political discourse.

But while Liberal MPs and candidates need to be prudent, he said they shouldn't be intimidated into reciting nothing but anodyne talking points.

"Canadians really value, I think, authenticity and spontaneity because they get too much that is pre-cooked, pre-canned drivel."