As she prepares to retire from the Senate after 22 years, Conservative Senator Marjory LeBreton says the wrenching controversy over expenses has brought the upper chamber to a turning point.

"The whole thing is laid bare and there's no place to go but up."

In an interview Tuesday with CBC News' Susan Lunn, LeBreton expressed regret that changes she made around transparency and accountability ultimately hurt the Harper government — but, as painful as the fallout has been, it was "the right thing to do."

LeBreton said the Conservative majority in the Senate had set out to clean up what some thought of as a "closed club," by deciding in 2010 to release senators' expenses on a quarterly basis. That, LeBreton said, is what triggered the media and public interest that eventually culminated in the Senate expense scandal.

"Unfortunately for [those senators], we changed the rules. It was a very difficult process for all of us, painful for some, but it was the right thing to do."

'Blindsided' by extent of scandal

It was LeBreton, as the government leader in the Senate at the time, who invited the federal auditor general in June 2013 to audit senators' expenses, following months of controversy over the expenses of now-suspended senators Mike Duffy and Patrick Brazeau, and now-retired former Liberal senator Mac Harb.

Senator Marjory LeBreton, who retires next month after a tumultuous close to her 22-year Senate career, said making the upper chamber more accountable was "the right thing to do." (Sean Kilpatrick/Canadian Press)

But LeBreton said that despite her attempts to promote accountability, she at times felt "blindsided," and did not anticipate how far-reaching the Senate expense scandal would be.

"I didn't know how many people the auditor general was ultimately going to find there was problems with. Actually I was quite surprised, I thought there would be fewer than that."

LeBreton also expressed dismay and disappointment that some had abused their office.

Pointing out that fewer than a thousand Canadians have served in the Senate since Confederation, she said "to blow an opportunity like that is just mind boggling to me.

"I cannot understand how people wouldn't take the opportunity that they're given and do good things. It's just something I don't understand."

LeBreton, who was named to the Senate to represent Ontario by former prime minister Brian Mulroney in 1993, defended the Senate appointments under Prime Minister Stephen Harper, saying that a vetting process can't single out people whose intentions are not honourable.

LeBreton stepped down as government leader in the Senate shortly after her decision to call in the auditor general, announcing in July 2013 that she would serve out her term as senator but no longer serve in Harper's cabinet.

"I took a lot of abuse in the past few years, people saying things that weren't so kind, but I just said 'too bad.' It was the right thing to do."

"If I've put the Senate on a new path of transparency and accountability, then I'm a happy camper."