For the first time since the integrity commissioner position was launched eight years ago, Ottawa city council is asking for the office's powers to be used against one of its own.

On Wednesday, council voted 18-to-6 in favour of requesting that integrity commissioner Robert Marleau investigate whether a member of council leaked a confidential memo about the city's $361-million lawsuit over the Rideau Street sinkhole to reporters.

The investigation could cost $25,000 or more, council heard, and there's no guarantee Marleau would discover anything. As well, Marleau — the city's first-ever commissioner — is retiring at the end of August, and it's unlikely his investigation would be completed by then.

The memo in question was sent to council and senior staff on the evening of May 10, and outlined how the city was planning to sue its insurers for the Confederation Line project for $361 million: $131 million for costs related to the sinkhole that the insurance companies refused; and another $230 million to cover a $230 million claim the LRT builders had filed against the city.

The Ottawa Citizen first reported the story on the evening of May 11, after the lawsuit was filed in court. CBC reported the details the following morning. Most of the information in the memo was contained in the publicly available statement of claim.

But some councillors who voted in favour of the investigation said the confidential memo contained information that could jeopardize the city's legal strategy. When asked what the problematic information was, city solicitor David White declined to discuss it, even though the contents of the memo have been publicly reported.

Coun. Eli El-Chantiry, who moved the motion that was seconded by Coun. Keith Egli, was dismissive of the potential cost of the investigation.

"We ask how much this is going to cost," he said. "Well, why don't we ask ourselves how much that leak is going to cost us?"

Those who voted against the inquiry said it would accomplish little and was taking attention away from revelations about just how much problems with the Confederation Line may have cost taxpayers.

"This just strikes me as a great big, colossal waste of taxpayers time and money and a distraction really from the main event, which is what is going on with our LRT," said Coun. Diane Deans. "I don't see that there's any outcome that is going to advance anything along the way."

Coun. Shawn Menard agreed.

"Why don't we try to be clear with the public? I'd say vote this motion down and let's try to be more transparent with the public about how their money is being spent."

Coun. Glen Gower, who voted in favour of the investigation, said that when he was a journalism student at Carleton University, there was a lot of discussion "about the openness of government, and transparency."

While he conceded that leaks can sometimes "be part of the political process," he said he asked himself, among other things, whether the information that was leaked provided "any public interest … or something that was was being intentionally hidden that could harm the public?"

"I don't think that's the case here."

In fact, the leaked memo was the first time the public had ever heard that the city incurred tens of millions in costs from the June 2016 sinkhole or that the LRT constructors, Rideau Transit Group, were blaming the city for the event. In fact, $60 million was held back on the final payment for the Confederation Line back in 2019, which people were told covered the city's costs for the late delivery.

Suddenly, taxpayers are discovering the problems with the LRT have cost at least another $131 million.