It is the million-dollar investigation that was labelled a witch-hunt and this week caused the WA Liberals and Nationals political pain by reinforcing their financial mismanagement when in government.

But ultimately the lasting legacy of the Langoulant report could well be as a noose around the McGowan Government's neck.

As you would imagine of a six-month investigation commissioned by Premier Mark McGowan into the previous Government's fiscal management, the report provides a scathing assessment.

Taxpayers might rightly ask whether they really needed to spend $1.1 million to tell them what they already knew — the former Barnett Government had a spending problem and lacked a plan.

Others have quipped the report appeared to be an exercise in throwing good money after bad.

Ultimately the Langoulant report does provide further insight and detail on exactly what happened in the more than eight years of former premier Colin Barnett's reign that led to WA's economic woes.

Political ammunition … for now

The report's findings have no doubt further damaged the previous government's financial record but ultimately its wide-ranging recommendations could cause a lot of headaches for Mr McGowan and his Government.

So much so that Liberal Leader Mike Nahan has gone from labelling the inquiry a witch-hunt to declaring he will use the report as "a roadmap" to hold the Government to account.

Opposition Leader Mike Nahan concedes the Barnett government should have revised the Royalties for Regions scheme. ( ABC News: Jacob Kagi )

After the report's release, Mr McGowan seized on it to embarrass the Opposition in question time and called on the Liberals and Nationals to apologise to West Australians for the debt and deficits they left to future generations.

"The former Government ignored long established practices, processes and conventions," Mr McGowan said.

"The special inquiry has revealed a culture of recklessness. Decision-making processes were flawed, financial discipline was non-existent and the cabinet failed to take responsibility.

"This should never happen again. My Government will apply appropriate rigour and scrutiny to financial decisions, we will strengthen governance, accountability and transparency across government."

The report was critical of the previous government's lack of transparency on major projects, saying accountability had been eroded because "commercial-in-confidence" had become a default response to withhold information.

High bar for transparency

A day after tabling the report, Mr McGowan was out announcing the changes his Government would make "to ensure the mistakes of the past are never repeated."

They included giving the Auditor-General access to Cabinet documents, greater transparency for reporting details on major projects and establishing guidelines on the disclosure of information which is "commercial-in-confidence."

"We think the default position should be that information is released unless there's a good reason not to," Mr McGowan said.

Since coming to office almost a year ago his Government has refused to release the exact sum of a sponsorship deal with a major telco for naming rights at the new Perth Stadium.

The government has refused to disclose exactly how much Optus paid for naming rights at Perth Stadium. ( ABC News: Jarrod Lucas )

It has also refused to reveal what taxpayers forked out to bring tennis superstar Roger Federer to Perth for the Hopman Cup, which included a trip to Rottnest for that now internationally famous quokka selfie.

At the press conference where he had just spruiked greater transparency and commercial-in-confidence changes, Mr McGowan was again asked by a journalist what the deal with Federer cost taxpayers.

It made for awkward scenes as Mr McGowan danced around the topic and refused to provide the figure.

"Sometimes there are reasons why you don't release information because it puts the state at a commercial disadvantage when bidding against other jurisdictions," Mr McGowan said.

Roger Federer was flown to Rottnest Island as part of a tourism deal with WA. ( Instagram: Roger Federer )

But he did say he could "absolutely guarantee" the commercial-in-confidence term would be used by his Government less than the previous government to withhold information.

Mr McGowan and his ministers can expect to see journalists and taxpayers waving around the Langoulant report in the future every time it refuses to release information.

The Government got a lot of political mileage out of the Langoulant report this week, but it might find some of the report's recommendations have set the bar unrealistically high for the future.

The Premier may end up wondering if the short-term political gain was worth it for what could end up becoming plenty of long-term political pain.