A draft European parliament inquiry into the dieselgate scandal has found the European commission guilty of maladministration for failing to act quickly enough on evidence that defeat devices were being used to game emissions tests.

The commission ignored evidence of emissions test cheating from its own science body, the Joint Research Centre (JRC), partly out of a desire to “avoid placing burdens on industry”, according to the draft report seen by the Guardian.

Brussels should have alerted EU states to the suspicions of its scientists and requested information on steps being taken to deal with vehicles that emitted more nitrogen oxide (NOx) in real-world situations than in tests. But it did not.

“Dieselgate would not have happened if our national governments and the European commission had acted on their legal and administrative responsibilities,” said Gerben-Jan Gerbrandy, the inquiry’s co-author.

“Our investigation points out that unnecessary delays in decision-making, negligence and maladministration have contributed to making this fraud possible,” he said.

The Guardian has learned that Antonio Tajani, the centre-right European People’s party (EPP) nominee for president of the European parliament in 2017, could be personally censured in amendments to the report, due to be debated early next year.

Antonio Tajani, the European People’s party nominee for president of the European parliament, will be personally censured in amendments to the report. Photograph: Patrick Seeger/EPA

Tajani, a former spokesman to Silvio Berlusconi, was the EU’s industry commissioner between 2009 and 2014. Some believe MEPs could say that during that time he failed to respond to pressure from the EU’s environment wing to act on the gathering scandal.

Bas Eickhout, a Green MEP, said: “I would find it very strange if the parliament, having concluded that there was maladministration, then allowed one of the responsible commissioners to become its president. If our amendment is passed, it will mean that Tajani’s candidature is unacceptable.”

Other planned amendments will call for a beefed-up, Europe-wide market surveillance authority, and surprise tests of cars already on the road. The measures could be added to legislation due to come before parliament this term.

The draft dieselgate report was written as a consensus document and recommends an internal EU inquiry to examine why the JRC’s detection of possible defeat devices in 2012 were not acted upon.

It also advocates putting air quality and car emissions under the control of one commissioner – instead of being split between two at present – and calls for a renewed focus on potential fraud by manufacturers of other consumer products.

The commission will not respond to the parliamentary report until it is formally released next month. But one EU source said: “Car manufacturers have an obligation to comply with the law. And national authorities and technical services must enforce the ban.

“We are following national authorities’ policing and enforcement of EU rules in the automobile sector very closely and have launched a number of infringement procedures in the area.”

The commission recently began legal action against several countries, including the UK, for failing to set up penalty systems to deter violations of emissions law in a move that won the current industry commissioner, Elżbieta Bieńkowska, grudging respect from Green MEPs.

Despite the VW scandal, 27 of the EU’s 28 states have taken neither financial nor legal action against car manufacturers, nor made mandatory recalls or retrofits of vehicles, nor withdrawn type approvals.

Sweden, the sole exception, began running an in-service test programme before it became an EU member in 1995.

France, Italy and Spain were spotlighted by the report for delaying real-world driving emissions standards and pushing for less stringent testing methods.

The dieselgate report condemned what it said was a standard reliance by national regulators on tests provided by car manufacturers’ certified laboratories that created potential conflict of interests.

Gerbrandy said: “Governments disregarded their legal duty to monitor and enforce the ban on defeat devices. There seems to be a blind trust in the good intentions of car manufacturers, especially when they have production plants in the country concerned. It is even more disturbing that a year after the dieselgate scandal very little has actually changed.”

On Tuesday, the EU’s technical committee on motor vehicles will vote on a commission proposal to extend real-world driving emissions (RDE) legislation to particulates. However this would still allow car manufacturers to overshoot the limit by 50%.