MONTREAL -- A former Liberal transport minister who spent seven years in the department in various capacities couldn't explain Wednesday why construction companies heavily donated to her party.

Julie Boulet also insisted in testimony at the Charbonneau Commission there was no favourable treatment for those who did.

Boulet became the first sitting provincial politician to take the stand at the corruption probe.

Her appearance came after the inquiry recently shifted to hearing testimony about illegal political financing, bid-rigging and spiralling costs in the awarding of provincial contracts.

Boulet, who was junior transport minister between 2003 and '07 and transport minister from 2007 to 2010, said she never favoured one firm over another.

That answer didn't satisfy the inquiry, which tried to ask in a number of ways why construction firms donated heavily if it served them no purpose.

"If you offered no special treatment for those who financed the party, why did they continue to finance your party year after year?," asked inquiry counsel Sonia LeBel.

"I can't answer you," Boulet answered repeatedly, adding on one occasion, "I followed the rules."

Boulet described herself as "hard-working, honest and rigorous" and said these characteristics led her into politics.

Her former chief of staff for 16 months in the mid-2000s previously testified at the commission that Boulet was a detail-oriented person who wanted to see figures and asked many questions before making decisions.

But in an often difficult day of testimony for Boulet, the inquiry called that rigour into question.

She wasn't even able to answer how much she spent on her most recent election campaign.

"You said you were a rigorous woman, but you don't know how much your campaign cost?" inquiry chair France Charbonneau asked her.

Boulet replied that she had an official agent who oversaw her campaigns. It was a similar delegation of duty when it came to fundraising -- a staff member handled the details.

Boulet told the commission that since first being elected to the legislature in 2001 she has never sold a Liberal party membership card, a fundraiser ticket or solicited a company for money.

"I've never done political financing," said Boulet.

The political veteran said a staff member would consult a list of donors and invite them to attend big ticket fundraisers in her riding twice a year.

Boulet said she never consulted the list, had no idea who gave what amounts and only had a rough idea about how much events brought in.

She testified she detested cocktail fundraisers and only attended out of a sense of duty.

"I went when I had no choice," Boulet said.

She claimed to be in the dark on her own party's political financing objectives.

Boulet said she found out about a $100,000 annual fundraising goal for each cabinet minister only when former colleague Norman MacMillan publicly announced the figure in 2009.

She later conceded she was aware of riding objectives but said her central Quebec riding was poor and didn't have a ton of fundraising dollars to go around.

Boulet said she entered politics to help people, not fundraise.

She said local politicians, all sitting members of the legislature, businesses and community groups often solicited her for Transport Department for help on projects.

A pharmacist by trade, she deferred to Transport Department officials who had the expertise and training.

And it was the bureaucrats who had final say.

"I never went against the experts from the department," Boulet said. "I had total confidence in these people."

One construction boss who was critical of political financing involving the transport minister's office under all political parties mentioned Boulet's name in his testimony this week.

Louis Marchand of Maskimo told the inquiry he declined an invitation from Boulet's office in 2004 to attend a $1,000 fundraiser. He said he wasn't happy with the number of non-tendered government contracts his firm was getting. The decision to not attend earned him a call from Boulet herself to express her disappointment.

Boulet said she did call him -- not to pressure him but to see if there was anything she could do to help.

She was re-elected for a sixth mandate in last month's provincewide vote but did not make it into Premier Philippe Couillard's cabinet.

Boulet returns to the stand on Thursday.