This is despite action taken after the dieselgate scandal, under which German carmaker VW falsified emissions data on its diesel vehicles, pretending they were cleaner than they are.
The company cheated by installing a piece of software into computers on its cars that recognise when the car is being tested - a so-called 'defeat device'.
Parliament's Greens/EFA group is now calling on the Commission to step up to the plate and launch infringement proceedings against member states which fail to take necessary action to ensure EU standards are complied with.
The demand comes just ahead of the two year anniversary of the scandal first breaking (19 September) and ahead of a debate on dieselgate during next week's Strasbourg plenary.
Parliament also launched a committee of inquiry into the scandal which heard evidence from industry experts and government ministers.
At a briefing on the issue on Thursday, Greens MEP Bas Eickhout said, "In the past, lawmakers have been too lax and lenient in addressing this issue and it has been left to the national authorities. But we are now calling on the Commission to state exactly what they expect member states to do."
He added, "Over 400,000 people die in Europe prematurely each year due to poor air quality and, basically, it is time for the Commission to step up to the plate."
He went on, "Dieselgate is still high on the agenda and the specific reason is that there are estimated to be 25 million diesel cars still on the road in Europe that still emit an excessively high level of nitrogen oxide (NOx) and therefore do not meet EU emissions standards."
Eickhout reminded reporters that in August, German car manufacturers and politicians held a diesel summit, agreeing to cut harmful emissions by updating software in vehicles.
The UK and France both announced plans to ban diesel cars by 2040 and manufacturers announced schemes designed to phase out diesel vehicles.
At the beginning of this month, the real driving emissions (RDE) test came into force across the EU, one of the measures agreed in the wake of the dieselgate scandal.
However, the Dutch deputy described the outcome of the Berlin summit as "disappointing", adding that national regulators "still hold their protective hand" over their respective car manufacturers.
German national and state governments and car makers have agreed to upgrade software on some 5.3 million diesel vehicles which have so-called defeat device, but Eickhout said the impact of this was highly doubtful and that more substantial retrofitting of the affected diesel vehicles will be needed.
He said that persistent breaches of NO2 limit values had been found in 28 German air quality zones, including Berlin, Munich and Hamburg.
The MEP went on, "You have to ask if the Commission considers the measures agreed at the German diesel summit last month to be sufficient to address the air quality problems in Germany."
The scandal first broke in 2015 when it emerged in the US that Volkswagen had installed defeat devices on some of its diesel cars which realised when a car was being tested for emissions.
They then turned on full pollution controls to meet the required standards but were not in use in normal driving conditions.
This meant that Volkswagen cars pumped out up to 40 times the permitted level of pollution in real world driving conditions - news which sent the company's share price plunging.
Volkswagen has admitted that while about half a million cars in the US were affected, as many as 11 million worldwide contained defeat devices.
At the briefing, Eickhout and his Greens colleague Claude Turmes also condemned the European response to the scandal compared with the US.
Turmes said, "The inaction in Europe compared to the other side of the Atlantic is shocking."
He pointed to the health costs of dieselgate and existing vehicles which still fail to meet EU standards, saying, "The consequences of one of Europe's biggest cases of industrial fraud for human health, air quality and Europe's economy have shown to be disastrous."
The US authorities had, he said, severely punished Volkswagen - including jailing one of the key organisers of the fraud - and used parts of the fines to invest in air quality measures.
Class actions have been launched in the US, but, he said, it had proved very difficult to do the same in Europe.
The Greens also disclosed an internal letter, dated 17 July, about dieselgate which was signed by European industry Commissioner Elżbieta Bieńkowska and sent to EU ministers in which she agrees on the need to remove non-compliant vehicles from the roads.
In the letter, she states, "What we have achieved with the new real driving emissions tests is not enough. We have to remove non-compliant cars from the market and circulation as soon as possible."
She goes on, "It is vital that measures are adopted in a consistent manner by all member states and that they are effective."
The official notes the significant efforts by the Netherlands, Germany and France regarding voluntary recalls but said that local diesel bans of the kind adopted in some countries, including Germany, should be avoided.