OTTAWA — The NDP launched a "roll up the red carpet" campaign Wednesday to abolish the Senate in the face of a growing spending scandal that has followed Prime Minister Stephen Harper to South America.

NDP Leader Thomas Mulcair used the Senate as backdrop to announce he would hit the road to win provincial and territorial support to open the Constitution to abolish the upper chamber.

Mulcair described the Senate as a dumping ground for party bagmen, political organizers and defeated candidates.

"The Senate cannot be reformed," Mulcair said. "It's become a scandal that won't go away for Mr. Harper."

Harper departed on a trade mission to Peru and Colombia on Tuesday after he described events in the Senate as a distraction. He was expected to take questions for the first time on events Wednesday.

His chief of staff resigned on the weekend after questions were raised about the appropriateness of gifting $90,000 to Sen. Mike Duffy to help the former journalist return money he collected in housing allowances.

Two other senators — Mac Harb and Patrick Brazeau — are also embroiled in the housing allowance controversy, and a third — Pamela Wallin — is awaiting the results of an audit into travel expenses.

Both Wallin and Duffy resigned from Conservative caucus to sit as independents. Harb, a Liberal, also sits as an independent as does Brazeau, who was kicked out of caucus over assault charges.

The federal ethics watchdog is investigating Wright's payout to Duffy.

A Senate committee that has been accused of whitewashing its original report into Duffy's expenses has decided to take another look at the books in light of new allegations Duffy was billing taxpayers for non-Senate business.