An independent inquiry into the procurement of the $4.4 billion New Generation Rollingstock, led by retired judge Michael Forde, found the design of the trains was flawed from "day one".

The trains had disability access issues, including the toilets and pathways being too small for wheelchairs, but they were rolled out in December 2017 as the NGR were needed for the Commonwealth Games timetable, despite a pending application for an exemption to the Australian Human Rights Commission.

Among the people interviewed during the inquiry were current Queensland Rail CEO Nick Easy, former QR chief executive Helen Gluer, former LNP transport minister Scott Emerson, former LNP treasurer Tim Nicholls, Premier Annastacia Palaszczuk and Deputy Premier Jackie Trad.

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Procurement for the NGR was unnecessarily prolonged and marred by delays, disruptions and failures to adhere to policies, guidelines and frameworks, the inquiry's report said.

The procurement process took five years - four years longer than it should have - after starting in 2008.

There was a project "pause" for six months in 2012, before which the NGR project was characterised by a "lack of rigour, continual slippages and missed milestones", which was during the Bligh Labor government.

The model was changed to a public-private partnership under the Newman LNP government, with the change coming so late in the process it created disruptions and difficulties for the two shortlisted proponents.

Changing the project lead from Queensland Rail to Projects Queensland, acting on behalf of Transport and Main Roads, in 2012 was disruptive and created animosity between the two agencies.

The disruption, break in continuity and resulting animosity may have contributed to non-compliance with disability access as a result of information not being transferred and not shared across agencies later in the project.

Decisions to allow non-compliant trains were made on the basis of incomplete information as those issues were not escalated to senior decision-makers.

A cost-saving decision to require only one toilet on each train at the leading end of accessible car B made it impossible for the trains to be fully disability compliant.

The decision was endorsed by the transport executive committee and former transport minister, Mr Emerson.

But the report said the decision was endorsed on the basis of incomplete information, as non-compliance issues were not escalated to senior decision makers.

"CBRC and the former minister for transport and main roads, who made decisions regarding the procurement of the NGR trains ... cannot fairly be blamed for the decisions," the report said.

The narrow gauge of the Citytrain network made disability compliance challenging but it was possible to design a technically compliant train.

The procurement process asked for non-compliant trains and the contract was awarded to Bombardier on the basis of non-compliant designs.

That means Bombardier was not to blame as they built the trains to the contract's specifications.

The subsequent design process did not effectively manage or resolve non-compliance.

A decision to remove QR as the project lead created a degree of resentment and animosity, resulting in a competitive relationship during the delivery phase.

"The tense relationship hindered the effective management and resolution of compliance issues," the report said.

There was a persistent failure to inform project governing bodies and senior executives of the issues regarding non-compliance with the disablity legislation.

The procurement and delivery of the NGR trains spanned from the Bligh Labor government, the Newman LNP government and Palaszczuk Labor government.

However, Mr Forde said people working in middle to lower management did not escalate problems higher up the chain and "were perhaps afraid of giving bad news at different stages".

Mr Forde said there also seemed to be an attitude of "it might be fixed down the track".

No specific consultation was held with the disability sector about the NGR during the procurement phase.

The report argued if the NGR project had undertaken genuine consultation before or early in the procurement process, it would have led to a highlighting of key accessibility requirements.

"It would certainly have been more cost effective than rectification of the trains," the report reads.

The inquiry made 24 recommendations, all of which were accepted by the Queensland government.

Work to fix the disability access issues will be carried out by Downer EDI at its Maryborough facility, with a full completion date expected in early 2024, at a cost of $335.7 million.

The modifications will include installing larger toilet modules in the middle carriages across the entire 75-train fleet to allow passengers who use mobility devices to access the toilet from both accessible carriages.

The number of priority seats will be doubled from 24 to 48 per six car train, and there will be revised seating layouts.

The Human Rights Commission earlier this year rejected a human rights exemption application by the state government over the trains' non-compliance with disability access laws.