New Brunswick Senator John Wallace is leaving the Red Chamber years before his mandatory retirement date because he is sticking to the pledge he made former prime minister Stephen Harper to only serve an eight-year term. Others appointed at the same time, however, say they have no plans to step aside.

Harper appointed 18 senators in January 2009 when there were fears the Liberals and the NDP would form a coalition to bring down the Conservative minority government. At the time, Harper had only appointed two senators and the Liberals held a numerical majority in the chamber.

In a statement sent from the Prime Minister's Office, Harper said all appointees were committed to helping implement the government's Senate reform agenda and would serve a limited, eight-year term as part of the push to change the upper chamber.

Independent Saskatchewan Senator Pamela Wallin, who was appointed alongside Wallace, said Tuesday there was "never a formal request regarding limiting length of service," at the time of her appointment. But she said she is a "firm believer" in the concept of term limits.

Wallin also said she has not yet served for eight years, as she was suspended from the chamber for roughly two years as a result of the Senate expenses scandal. The RCMP announced in May it wouldn't press criminal charges against Wallin for irregularities in her expenses.

Independent Saskatchewan Senator Pamela Wallin, who was appointed alongside Wallace, said there was 'never a formal request regarding limiting length of service' at the time of her 2009 appointment. (Adrian Wyld/Canadian Press)

"In several years, when I have completed at least eight years of service, I will assess the progress toward an independent Senate to which I am firmly committed," she told CBC News. "And at that time will consider how I can best serve my province and my country."

Harper's plans for Senate reform were ultimately derailed by the expenses scandal, as well as a Supreme Court reference, which said term limits of any sort would require a constitutional amendment.

Under the current rules, senators are forced into mandatory retirement when they turn 75.

Wallace is the only one out of the 13 remaining senators appointed in that round who has publicly said he will resign.

"For me, eight years for any appointed position is lengthy enough. That was the mindset I had back in 2009 and I believe I have to follow through on it," Wallace said in an interview with CBC News. "All of a sudden I looked at the calendar ... it's not more complicated than that."

The 67-year-old said he will formally resign on Feb. 1, 2017.

Wallace said he doesn't think other appointees should be forced to retire, although he said there was a clear "expectation" from Harper that they all agree to the concept of term limits.

"I'm not suggesting that anybody should be influenced or follow what I've done; they may look at this differently — it's up to them," he said, adding there are senators who have served for 20 years that are still making meaningful contributions.

'Never asked to arbitrarily resign'

At least three other Conservative senators appointed in January 2009 said Tuesday they have no intention of stepping aside.

"I still have things to do and look forward to fulfilling the commitment I made to serve until I was 75," B.C. Senator Nancy Greene Raine said in an email.

Senator Nancy Greene Raine told CBC News she is planning to continue to serve until she is 75, which is the mandatory retirement age for the upper chamber. (CBC)

Nova Scotia Senator Michael MacDonald said he was "never asked to arbitrarily resign after eight years."

"When I was appointed, I was asked if I would support elected term limits for senators if [Harper] could accomplish it. I said that I would, and would respond accordingly if that change was enacted. The Supreme Court made it very clear in the fall of 2014 that the federal government's approach was unconstitutional. Like every senator in the chamber, I have been appointed according to the law as stated in the Constitution."

Ontario Senator Nicole Eaton also said she has no plans to retire and that she was only "generally asked whether [she] agreed with Senate reform" at the time of her appointment.

Quitting the Conservative caucus

Wallace left the Conservative caucus late last year to sit as an Independent, citing irreconcilable differences between himself and Conservative Senate Leader Claude ​Carignan.

The former lawyer was also one of the most vocal defenders of Senators Mike Duffy, Pamela Wallin and Patrick Brazeau during the expense scandal.

During Tuesday's interview, Wallace called the suspension vote one of his darkest days as a senator.

"I didn't agree with the motions of suspension that were placed before the Senate chamber, I didn't agree with the lack of due process and fairness," he said.

"I tried to influence my colleagues [against] the need for something of this nature. I would never excuse inexcusable behaviour, but it was the rush to judgment."

Wallace penned a note in 2013 outlining what he saw as problems with the Senate's rules around housing allowances — a letter that was later made public at Duffy's trial.

He chided the Senate's internal economy committee for referring Duffy's case to the authorities, saying it was clear that issues of "geography" and the institution's own ambiguous rules had prompted an administrative problem in the first place.

Wallace said his position was vindicated after Justice Charles Vaillancourt delivered a scathing rebuke in Duffy's case, questioning the motivations of the Senate leadership in carrying out the suspensions.

The P.E.I. senator ultimately had all 31 criminal charges of fraud, breach of trust and bribery dismissed. After the acquittal, Wallace unsuccessfully pushed the chamber's internal economy committee to reimburse Duffy's pay.