The Senate is going to start clawing back a portion of Mike Duffy's salary after the P.E.I. senator refused to repay nearly $17,000 in disputed expense claims before Saturday's deadline.

Though Duffy was cleared last April of all 31 charges of fraud, breach of trust and bribery related to his expenses, the Senate has since demanded he pay back thousands in expenses after new information came to light during his trial.

"The deadline to repay or indicate that he was opting for arbitration was Saturday. And, as you know, Senator Duffy indicated he would do neither," said Jacqui Delaney, a spokeswoman for Senator Leo Housakos, chairman of the upper chamber's internal economy committee.

"As per the independent dispute resolution process, the Senate now must offset Senator Duffy's salary," Delaney said in an email to CBC News on Monday.

While Duffy was cleared of all criminal charges, Senate officials have taken issue with a number of expenses raised during his trial.

The Senate has deemed ineligible certain expenses Duffy filed between the period of March 5, 2009, and Sept. 13, 2012, for pictures, makeup and a personal trainer.

Donald Bayne, Duffy's lawyer, said his client would not pay the money back and that there was no need for arbitration because a judge issued a resounding not-guilty verdict.

But the Senate is standing firm and will proceed with automatically deducting $16,955 from Duffy's paycheque.

Delaney could not say on what date the Senate would start to claw back a portion of Duffy's salary.

Bayne was not immediately available for comment.