Prime Minister Justin Trudeau has lauded various police investigations and audits of questionable spending by dozens of Senators as necessary steps to bring about "greater accountability" in the unelected Senate.

Mr. Trudeau, who was in New York to meet United Nations Secretary General Ban ki Moon, was asked Wednesday whether RCMP criminal probes of 30 current and past senators were worth the cost and effort, given a report in The Globe and Mail that all of them are expected to be cleared of wrongdoing.

The Globe reported Wednesday the RCMP has already exonerated 24 of 30 Senators who expenses were flagged by the Auditor General and is expected to clear the remaining six.

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"I think the travails of the Senate and what senators went through over the past years highlighted the need for greater transparency, greater openness and greater accountability and indeed a distancing from partisanship and patronage that has defined the Senate," Mr. Trudeau told reporters.

The Red Chamber has taken a series of steps to tighten its spending rules and to post the expenses of all 104 senators online.

"The various investigations and concerns and issues highlighted have led us to a place where I think we are on the right track," Mr. Trudeau said.

The Liberal government has vowed to make the Upper House less partisan by naming independent senators.

The RCMP has ruled out pursuing criminal investigations against 24 of 30 current and former senators whose expenses were flagged by Auditor-General Michael Ferguson after a two-year forensic audit of the Red Chamber, sources say.

The Auditor-General's comprehensive audit, released last June, named nine current and former senators whose files warranted RCMP investigation and another 21 whose expenses were questionable. The Mounties decided to review the expenses of all 30 and sources said those probes are nearly complete.

"The RCMP has exonerated – in writing – 24 of 30 senators and there are six files left," a source told The Globe and Mail. "They investigated thoroughly and they did not find anything to warrant any formal investigation of anyone." Another source said RCMP investigators expect that the remaining six senators will also be cleared of any wrongdoing, citing a lack of "strong evidence." Unlike the case of Conservative Senator Mike Duffy, the source said the RCMP does not have detailed diaries of these senators to help in their probe.

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Five of the senators still under investigation were on the list of the nine that the Auditor-General recommended to be referred to the RCMP, according to two sources. They are: Liberal Senator Colin Kenny and former senators Rose-Marie Losier-Cool (Liberal-N.B.); Marie Charette-Poulin (Liberal-Ont.); Donald Oliver (Conservative-N.S.); and Gerry St. Germain (Conservative-B.C.).

Conservative Senator Pierre-Hugues Boisvenu and retired Liberal senators Rod Zimmer, Bill Rompkey and Sharon Carstairs received letters from the Mounties saying there was no evidence to mount a criminal investigation.

The expenses of a sixth senator, which were questioned by the Auditor-General, are also being reviewed by the RCMP. The Globe and Mail was unable to confirm the name of that senator. Sources say the senator has not yet been interviewed by the RCMP.

"Generally, the RCMP and Crown don't like to prosecute unless they have a good case," former House of Commons law clerk Rob Walsh said. "I suspect after Duffy, they don't feel they have good enough cases to warrant prosecution." Mr. Duffy was charged with 31 counts of fraud, breach of trust and bribery. Justice Charles Vaillancourt is set to deliver a ruling in the case on April 21.

The RCMP would not comment on the state of its Senate investigation and when it expects to close its files. "Generally, only in the event that an investigation results in the laying of criminal charges, would the RCMP confirm its investigation, the nature of any charges laid and the identity of the individual (s) involved," RCMP Corporal Valerie Thibodeau said in a statement to The Globe and Mail.

Some of the senators whose expenses were questioned repaid the money while others disputed the Auditor-General's findings. Former Supreme Court of Canada justice Ian Binnie took on the task as a special arbitrator to review the expenses of 14 senators who challenged the Auditor-General's conclusions.

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The Senate internal economy committee will release Mr. Binnie's report on Monday, a day before the federal budget is tabled. The report's conclusions are final and there is no avenue of appeal within the Senate.

"There is nothing to stop them from going to court but I doubt anyone will because of the cost," Mr. Walsh said. "Probably everyone, including the RCMP, hopes the whole damn thing will go away."

Mr. Ferguson's office audited the expenses of 116 senators between April, 2011, and March, 2013, at a cost of $24-million. Auditors reviewed 80,000 transactions and flagged the expenses of 30 current and former senators from both parties, worth about $992,000.

The Senate invited the Auditor-General to conduct the forensic audit in response to a public outcry over spending revelations involving Mr. Duffy, Conservative Senator Patrick Brazeau and then-Liberal Senator Mac Harb. All three face criminal charges of fraud and breach of trust.

Conservative Senator Pamela Wallin is also under criminal investigation over allegations of fraud and breach of trust. The investigation has been going on since 2013. The investigation was wrapped up and referred to the Crown but no charges have been laid. A source suggested there may not be enough evidence to lay criminal charges.