Rod Zimmer, a retired Liberal senator from Manitoba, is being flagged for questionable expenses of more than $176,000 and is facing the prospect of an RCMP investigation.

In a scathing audit of Senate spending to be made public next week, Zimmer weighs in with the single highest sum of questionable claims: $176,014.

He is one of several senators with six-figure problems identified in auditor general Michael Ferguson's report.

Auditors allege Zimmer lived primarily at a home in Ottawa that he claimed as a secondary residence, a classification that allowed him to collect a housing allowance.

The audit also alleges Zimmer and his wife, Maygan Sensenberger, charged the Senate for $2,072 over two years for taxis in Ottawa that were in fact used for personal trips.

Zimmer is disputing the claims in the report, portions of which have been viewed by The Canadian Press.