And an overwhelming number of Canadians questioned want to be able to check up on them by requiring all parliamentarians to publicly post all their expenses online.
The Canadian Press Harris-Decima survey results come after weeks of sustained controversy over questionable living and travel expenses claimed by four senators — Mike Duffy, Pamela Wallin, Patrick Brazeau and Mac Harb.
While only unelected senators have been implicated in the expense scandal thus far, the poll suggests it has blackened the reputations of MPs as well.
A whopping 86 per cent of respondents — including overwhelming majorities in all regions and across all age groups and party affiliations — feel it's likely that MPs and senators are claiming improper expenses. Of those, 56 per cent feel it's very likely.
The telephone survey of 1,005 Canadians was conducted June 6-9 and is considered accurate within plus or minus 3.1 percentage points, 19 times in 20.
Fully 89 per cent believe all expenses claimed by MPs and senators should be available for the public to view online.
"In public opinion terms, this is as close as you come to unanimity," said Harris-Decima chairman Allan Gregg.
"Virtually everyone thinks parliamentarians are cheating. Virtually everyone want transparency. Therefore, the only way parliamentarians can convince the public that they are not cheating is to show them that they aren't."
The Senate has taken some steps aimed at restoring public confidence in the upper chamber. It has toughened up the rules for senators' expense claims and it has called in the auditor general to scrutinize those claims.
Liberal Leader Justin Trudeau has proposed online posting of MPs' expenses and regular examinations of House of Commons expenses by the auditor general.
However, an attempt to win unanimous consent for his proposals failed earlier this week when New Democrat MPs voiced their objections. NDP Leader Tom Mulcair later referred to Trudeau's move as a "stunt" aimed at deflecting attention from the scandal involving Liberal and Conservative senators.
Mulcair has noted that an audit of the Commons last year gave the elected chamber a "clean bill of health."
Trudeau is promising that Liberal MPs will start posting their expenses in the fall, whether or not other parties follow suit.
The ruling Conservatives have said they support the idea.
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