The investigation into allegations of illegal financing within the Quebec Liberal Party (PLQ) between 2001 and 2012, under then-leader Jean Charest, is over.

Quebec's anti-corruption unit (UPAC), alongside the province's Crown prosecutor's office (DPCP), made the announcement Monday that it is ending Operation Mâchurer eight years after it was formed.

The investigation targeted Charest, as well as Liberal fundraiser Marc Bibeau, in determining whether criminal offences were committed in connection with the Liberal Party's fundraising activities.

More than 300 witnesses were interviewed as part of the investigation, which was launched in April 2014, according to UPAC.

Charest has, over the years, demanded that UPAC end its investigation, most notably in 2020 when he apparently considered returning to politics by running for the federal Conservative leadership.

Now, two years later, Charest is once again considering a run for the party's top job after former leader Erin O'Toole was voted out by his caucus earlier this month.

In a statement Monday, Charest wrote that the investigation has "weighed very heavily in my personal life, the life of my family, my political colleagues and my colleagues at work."

The former premier has returned to practicing law since leaving politics.

"The pursuit of this investigation made no sense and has been for me and my family an injustice that lasted for almost eight years," he wrote.

He notes he has just learned about steps already taken by UPAC, including an earlier decision to "submit the information that they had gathered in the course of the investigation... to a panel of independent experts."

"Following the opinion of the expert panel, the decision was made to end the investigation," Charest wrote.

He adds that he and his family "wish to thank our advisors, colleagues and friends who never ceased to support us."

VOCAL SUPPORT IN CONSERVATIVE PARTY

Conservative House leader Gérard Deltell notes the timing is good for UPAC to drop their investigation, especially if Charest decides to run for the party's leadership.

"There is some attraction, curious positivity about him and that will be very interesting if Mr. Charest decides to run -- this is what I hope for, by the way," he said. "I know that he is exactly the person that I want to rally people in our party, to unite our party and to attract Canadians to our party."

Deltell points out the decision to drop the investigation was not a political one.

"The decision has been made by the Justice Department, this is an administrative and judiciary decision," he said. "Obviously the impact on that is that now Mr. Charest can focus 100 per cent for the future of this party, for the future of this country."

Deltell says he wholeheartedly believes Charest is the "best man" to go up against Justin Trudeau in the next federal election, slated for Oct. 20, 2025.

REASONS FOR DROPPING INVESTIGATION AREN'T PUBLIC

In its press release Monday, the Crown prosecutor's office explains UPAC had asked for its "legal opinion" on the investigation.

"Drawing on the experience and expertise of its members, the review committee conducted a rigorous analysis of the evidence submitted by UPAC," the DPCP states. "The DPCP is regularly consulted by police forces when they wish to obtain a legal opinion in the context of an investigation. However, the decision to terminate a police investigation and whether or not to submit a request to the DPCP to initiate legal proceedings remains the prerogative of police forces."

The DPCP notes legal advice is considered confidential and cannot be revealed.

-- with files from CTV's Selena Ross.