The Liberals have written to the RCMP asking them to investigate the Conservative party's alleged role in a payment scheme involving Sen. Mike Duffy.


Liberal Sean Casey sent a letter to RCMP commissioner Robert Paulson asking the force to probe whether someone in the party promised to pay off Duffy's contested living expenses.


Casey points to an RCMP affidavit filed in court last week, which suggests party fundraiser Sen. Irving Gerstein was prepared at one point to use party funds to reimburse Duffy as one of a number of conditions he had laid out in an agreement to pay back his expenses.


The Liberals point to section 16 of the Parliament of Canada Act, which makes it illegal to give a parliamentarian money in an attempt to influence them.


The Conservatives have underlined that only two people are under investigation — Duffy and Prime Minister Stephen Harper's chief of staff.