One of the Conservative Party's top spokesmen on law-and-order issues will face an RCMP investigation over his Senate travel claims related to his work on behalf of victims of crime, sources said.

Now sitting as an independent, Pierre-Hugues Boisvenu is seeking to show that he did not commit a crime in his handling of his Senate expenses. In a statement on Friday, he said he will "reply" to the Auditor-General's findings next week, after the report is officially released to the public.

Read more: The nine senators whose expenses are crossing onto the RCMP's radar

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A Senate official said the Auditor-General raised questions over travel expenses related to Mr. Boisvenu's work with the Murdered or Missing Persons' Families Association, which he founded in 2005. Mr. Boisvenu launched the group three years after his daughter was abducted, raped and murdered by a repeat offender.

Mr. Boisvenu left his position as the association's president when he was appointed to the Senate in 2010, but he stayed on as a special adviser. One of the issues that has been flagged by the Auditor-General, and will now be examined by the RCMP, is whether expenses charged to the Senate should have instead been claimed with the association, the source said.

The disputed amounts include nearly $40,000 in mileage, accommodations and per diems that were allegedly related to his work for the association.

In addition, Senate sources said Mr. Boisvenu is facing questions over living expenses that were incurred during his divorce. Last year, the Senate ethics officer said Mr. Boisvenu claimed living expenses for a period of time in which he stayed at the house of his girlfriend, who was also one of his employees. He has reimbursed the expenses.

During his time in the caucus, Mr. Boisvenu was frequently called upon to promote the Conservative government's law-and-order agenda, especially in Quebec where the party has few MPs. Mr. Boisvenu, who is from Sherbrooke, announced Thursday night that he has resigned from the Conservative caucus.

In the report that will be officially tabled on Tuesday, Auditor-General Michael Ferguson is calling for a complete overhaul of the Senate expense system.

"The weaknesses and problems uncovered in the course of this comprehensive audit of senators' expenses call for a transformational change in the way expenses are claimed, managed, controlled, and reviewed," Mr. Ferguson wrote in the report, a portion of which was seen by The Canadian Press.

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The audit is recommending that an independent oversight body of experts be established to decide whether an expense claim falls inside or outside Senate rules. It also calls for regular, outside audits of spending to promote "diligence and discipline" from senators and staff.

Over all, the Auditor-General has called for the file of seven retired senators and two sitting senators to be referred to the RCMP. In addition, the Auditor-General has raised questions about the expenses of 21 other senators. A Senate official said the total of disputed expenses comes in at $1-million.

The other sitting senator whose case is being referred to the RCMP is Colin Kenny, in relation to $36,000 in travel claims. Appointed as a Liberal, Mr. Kenny has long been one of the party's strongest voices on issues of security and defence, as well as a frequent critic of the RCMP leadership. On Friday, he said in a statement that he will "defend himself and fully expects to be vindicated at the conclusion of the process."

Another case that is being referred to the RCMP involves Rod Zimmer, a retired Liberal senator from Manitoba, who weighs in with the single highest sum of questionable claims: $176,000. Mr. Zimmer, who is disputing the findings, is facing questions over housing allowances and taxi charges, which were allegedly for personal trips.

The Auditor-General has also raised questions about the expenses of three top Senate officials: Conservative Speaker Leo Housakos, Conservative Leader in the Senate Claude Carignan and Opposition Leader James Cowan. All three of them were privy to the findings of the Auditor-General this week, and helped to create an arbitration process by which senators will be able to dispute the findings.

It is clear a number of senators do not believe the Auditor-General should have the last word on the validity of their expenses. Both Mr. Housakos and Mr. Cowan have said they will challenge the findings through a new arbitration process – overseen by former Supreme Court judge Ian Binnie – that they were personally involved in setting up.

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In the case of Mr. Carignan, the money has already been reimbursed by one of his staffers, whose travel expenses were deemed invalid.

Another defender of law-and-order in the Senate's Conservative caucus, retired police officer Jean-Guy Dagenais, is also planning to go to arbitration over $3,500 in disputed travel claims. "There is no doubt he will contest it," a Conservative official said.