The Senate's internal economy committee has accepted a plan by the federal auditor general to review all senators' expenses, including travel and office expenses, CBC News has learned.
Sources have told CBC News that senators will be required to co-operate.
Auditor General Michael Ferguson was first called to meet with the Senate's committee on internal economy in June, in the wake of the committee's reports on independent audits of expense claims by senators Patrick Brazeau, Mike Duffy and Mac Harb.
That committee issued a report on an audit of Senator Pamela Wallin's travel expenses this week.
Elizabeth Marshall, who is head of an audit subcommittee, told members of the larger internal economy committee when it met this week to discuss the Wallin report that the auditor general had a comprehensive plan to review all senators' expenses.
Marshall will be the liaison with the auditor general's office to ensure senators and Senate finance staff comply with the audit. Marshall is herself a former provincial auditor general.
CBC News has also learned that members of the committee this week discussed taking steps to put senators on a paid leave of absence, or suspend them from legislative duties such as votes and committee work, if they are under criminal investigation. It is unclear whether this will come before the full Senate when it resumes sitting in the fall.
(Brazeau was suspended by a vote of the Senate earlier this year, after he was charged with assault and sexual assault. His case is before the courts.)
Ferguson told reporters in June he would have to decide on the scope of a Senate audit and would then discuss an audit plan with the clerk of the Senate and the Senate's audit sub-committee to explain its objectives.
A spokeswoman for the auditor general said this week the office could not comment on the scope of the audit before the actual audit report is issued, but confirmed it was underway.
"We have begun planning. The audit is underway. We're not speculating on a completion date," Ghislain Desjardins told CBC News on Wednesday.
After the June meeting with the Senate committee, Ferguson said an interim report might take 18 months to complete, although he added that reports could come in different phases, and the Senate could be updated as the work takes place.
Ferguson first raised questions about a lack of documentation for some senators' expenses in June 2012.