The former lawyer for the Prime Minister's Office says the Conservative government has lost the moral authority to govern, and he's voting for change this election.

Benjamin Perrin says in a statement that based on what he's personally seen and experienced, he felt there was no other choice but to abandon his lifelong Conservative vote.

"Last week, I voted in an advance poll for change," Perrin said in a statement.

"As a lifelong conservative I never thought that would happen. But after what I've personally seen and experienced, there was no other choice. The current government has lost its moral authority to govern."

Perrin is currently a University of British Columbia law professor, on parental leave. He lives in the riding of Vancouver Kingsway. He did not specify for whom he cast a ballot, but said he voted "strategically."

Perrin worked in the PMO back in 2012-13, and was part of the staff that dealt with the scandal surrounding Senator Mike Duffy's contested living expenses.

Bombshell testimony at Duffy trial

But Perrin very publicly broke ranks with the government this August when he testified at Duffy's fraud and breach of trust trial.

He said that Harper's most senior aide Ray Novak was told during a meeting about former chief of staff Nigel Wright's secret repayment of Duffy's $90,000 in expenses.

"Because it was so surprising to me, I immediately looked to my right to see Mr. Novak's reaction and he didn't have any reaction to that information," Perrin said during his testimony.

Novak, who currently works as a senior campaign director, has denied that he knew; and Harper has backed his version of events.

Perrin also testified that he disagreed with Harper's assertion that an individual who owned $4,000 worth of property in a province met the constitutional requirement for representing that province in the Senate.