New Democratic Party leader Thomas Mulcair speaks during Question Period in the House of Commons on Parliament Hill in Ottawa February 27, 2013. (REUTERS/Chris Wattie)

OTTAWA - NDP Leader Thomas Mulcair isn't buying the outcome of a Senate investigation that cleared all but four unelected members of the Red Chamber of misusing tax dollars.

Senate leadership was in hyper drive Thursday trying to convince Canadians that only a foursome will face further scrutiny by outside auditors over the $22,000-a-year housing allowance and travel bills.

Media reports have suggested that at least 46 senators have been quietly returning tax dollars since 2010.