Three former staffers in the Prime Minister’s Office have hired high-priced Toronto law firms as the RCMP investigates a $90,000 cheque Nigel Wright wrote to Sen. Mike Duffy.

CTV News has learned that David Van Hemmen, Chris Woodcock and Benjamin Perrin have retained the legal services of three Toronto firms that charge hundreds of dollars per hour -- and taxpayers are footing the bill.

The federal government typically uses Justice Department lawyers, but outside lawyers can also be hired.

The Canadian Taxpayers Federation decried the use of Toronto law firms.

“The Justice Department should be looking after them, not a bunch of high priced Bay Street lawyers,” said the federation's director Gregory Thomas

Perrin served as special counsel to Prime Minister Stephen Harper. A sworn RCMP affidavit includes an email trail that suggests Perrin and Conservative Party lawyer Arthur Hamilton were involved in the secret deal that would see Duffy’s ineligible expenses covered by Harper’s then-chief of staff Nigel Wright.

The RCMP documents suggest that two others in the PMO were aware that Wright personally provided the money to repay Duffy's expenses: Wright's assistant David van Hemmen and Chris Woodcock, the PMO’s former director of issues management.

The affidavit also alleges that PMO staffers exerted influence over the Conservative Senate leadership in order to whitewash a Senate report on Duffy’s expenses.

The allegations in the affidavit have not been tested or proven in court.

Wright, the man at the centre of the RCMP investigation, is paying his own legal fees.

Meanwhile, a Conservative MP is preparing to introduce a bill that would give party caucuses the ability to vote out their leader, among other powers.

Michael Chong’s private member's bill proposes to limit the power of the prime minister and his office. If passed, it would not take effect until after the next election.

Observers say the mere introduction of the proposed legislation sends a signal of discontent within the Tory backbench.

With a report from CTV’s Deputy Ottawa Bureau Chief Laurie Graham