The Auditor-General has red-flagged the expenses of the top three Senate officials who are overseeing the Red Chamber's response to the still-unreleased report, sources said.

The revelation is raising new questions over the Senate's ability to clean up its internal mess, as the senators who will address the controversy are themselves facing negative findings in the audit.

The audit is scheduled to be made public on Tuesday, but some of the findings started to leak out Thursday as the Auditor-General sent its report to key Senate and government officials.

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The Auditor-General has called for reimbursements from Conservative Speaker Leo Housakos, Conservative Leader in the Senate Claude Carignan and Opposition Leader James Cowan. The three are among the 21 senators who will be asked to reimburse money to taxpayers, if they have not already done so.

However, they are not among the nine whose cases are expected to be referred to the RCMP. Sources said the Senate will be referring the cases of one current Liberal and one current Conservative senator, as well as the cases of five retired Liberals and two retired Conservatives.

In a statement late on Thursday, Conservative Senator Pierre-Hugues Boisvenu said his case had been referred to the RCMP and he was leaving the party's caucus. Mr. Boisvenu was a prominent supporter of victims' rights appointed to the Senate by Prime Minister Stephen Harper in 2010.

The current Liberal senator whose‎ case is being referred to the RCMP is Colin Kenny, a Senate official said.

A Senate official confirmed the RCMP will also be asked to look into the cases of the following retired senators: Conservatives Don Oliver and Gerry St. Germain, as well as Liberal appointed senators Rod Zimmer, Rose-Marie Losier-Cool and Marie-Paule Charette-Poulin. CTV News reported the following Liberal appointed senators are also on the list: Sharon Carstairs and Bill Rompkey.

Mr. Housakos, Mr. Carignan and Mr. Cowan were all involved in setting up an independent arbitration process – overseen by former Supreme Court judge Ian Binnie – by which senators will be able to challenge the findings of the Auditor-General.

Mr. Carignan's problems stem from an employee's travel expenses, totalling $3,000, which have been reimbursed and will not be disputed.

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The case of Mr. Housakos involves a discrepancy between contracts and invoices related to media monitoring, with Mr. Housakos expected to go to arbitration on the $6,000 dispute.

"I think the auditor is being, in my particular case, nit-picky," Mr. Housakos told The Canadian Press, arguing that his contracting arrangements actually saved the Senate money.

"I've done nothing but be transparent. These were two errors discovered by the Auditor-General that had no malintent."

Mr. Cowan told reporters he has a "respectful disagreement" with the Auditor-General over $10,000 in travel claims. He said the 2011 trips were related to his Senate duties, and that he will bring the matter to "the arbitration process that we have set in place."

Over all, the value of the controversial expenses flagged by the Auditor-General comes in at less than $1-million, with the worst case amounting to about $130,000, a Senate official said.

The Senate spending scandal has already engulfed one retired and three suspended senators, including former TV journalist Mike Duffy who is currently on trial on 31 charges in Ottawa. Former broadcaster Pamela Wallin is still under RCMP investigation, while suspended senator Patrick Brazeau and retired senator Mac Harb are awaiting their respective trials on fraud charges.

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There are officials in the Senate, however, stating that anyone with a negative finding in the audit should not be involved in the chamber's attempts to redress its reputation. In particular, there are concerns about the arbitration process created by Mr. Carignan, Mr. Housakos and Mr. Cowan.

"They created a process of which they can now avail themselves," a Senate official said.

A Senate source said the three senators a number of weeks ago took over the process of responding to the report from three other senators – Conservatives Beth Marshall and Larry Smith and Liberal George Furey – whose expenses were not found to be a problem by the Auditor-General.

Before its public release, the Auditor-General's report is being shared "within a very tight group of people," as Conservative and opposition senators prepare for the tabling of the explosive document.

"The goal is to showcase a common front when the report is released," a Senate source said.

The arbitration process will not affect the referral of alleged cases of financial wrongdoing to the RCMP, but will apply to current and recently retired senators who want to challenge the Senate's attempts to get its money back.

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Senate officials decided to create the arbitration system to settle the legal questions that will come from the line-by-line audit, including whether the senators were fulfilling parliamentary duties when they incurred controversial expenses.

Should the Auditor-General recommend that the Senate refer specific files to the RCMP, Mr. Housakos said last week the Senate will comply. He said final word on whether or not senators must pay back money will rest with the Senate's internal economy committee. Still, he added that senators have agreed to give Mr. Binnie the authority to rule on disputes.

Retired senators who participate in the process will have to agree in advance to adhere to the findings of the "binding arbitration." If they refuse to participate, they will face a lawsuit, a Senate official said.

In a statement, Mr. Binnie said he will work at arm's length from the Senate and evaluate each claim individually after hearing from both the senator and the Senate administration. "I am satisfied that this procedure is independent, fair and impartial," Mr. Binnie said. "Every citizen has the right to due process. The Senate arbitration process ensures this."

His findings will be made public.

Allowing for arbitration is a departure for the Senate: When four senators were suspended without pay in 2013 for their controversial expense claims, they did not have access to an independent review process.