Former Queensland Premier Anna Bligh has admitted the Queensland Government bought the wrong system to run its $1.2 billion health payroll, leading to a long-running and expensive debacle.

Speaking at the Gartner IT Infrastructure, Operations, and Datacentre Summit on Tuesday, Ms Bligh said the implementation in 2010 of a new payroll system turned into a “catastrophic disaster”.

The Government bought the wrong IBM product, and while trying to make it saw 74,000 health staff overpaid, underpaid, or not paid at all.

“The single biggest failure of the project was failure around managing the program and governance of it,” she said.

“There was no real clarity of governance. There was one part of the government that was responsible for whole of government IT in a shared service provider model, and then we had the line agency Queensland Health,” the former premier said.

“Between those two agencies there was not a single point of accountability. So everybody was in charge, which ultimately meant nobody was.”

So, when Queensland Health thought it was buying a one-for-one replacement of its previous system, things went wrong.

“We basically got the product we bought, but we bought the wrong one, or we bought one that was not fit for purpose,” Ms Bligh said.

She said the Government also failed to fully consider the complexity of the job, especially the system that must work between almost 200 industrial agreements, which created at least 24,000 possible combinations of allowances and conditions for it to handle.

Others accused IBM of failing to sell the Government the appropriate product.

Ms Bligh said if she had the chance again, she would have used a single external party which could fully grasp and oversee the project.

“There was so many people who had been so close to this project, both in IBM and SAP, and within the government agencies, when it came time to unpick what was wrong they couldn't see it, and they were very unwilling to allow themselves to contemplate that they might have made a mistake,” she said.

But admissions aside, the current Queensland government sought legal action against IBM over the project late last year.

The legal action was sought by LNP Premier Campbell Newman, who has since been replaced by the new Labor Premier Annastacia Palaszczuk.

It is unclear whether the case will continue, but it had previously sought compensation for the health staff that were wrongly paid.

“Queenslanders were wronged, we believe, in the pay affair, and we intend to recover money for them - the taxpayers - the men and women of Queensland,” then Queeensland premier, Campbell Newman, said in December last year.