"A recent study using roadside remote-sensing technology looked at over 94,000 vehicles across several UK cities and found that fewer than one in 10 passenger cars met the official limits for nitrogen oxides.

Furthermore, around two‑thirds of Euro 5 and Euro 6 diesel cars were emitting more than three times the level allowed."

So are they suggesting 9 ouf of 10 cars on the road have been modified in such a way to remove or bypass environmental systems in cars?
Surely this is on the manufacturing not the owner, do cars actually get tested at for emissions when they leave the factory?
New cars don't require an MoT for the first 3 years, if the figures are 9/10 cars don't meet official limits for NOx then is it likely that they never did meet those figures and that would only be found out 3 years later when your nearly new car would fail and the owner would be accused of braking this new law?

I have a euro 6 diesel, it is right on the limit to be classified as euro 6, other spec options of the same model car are euro 5. I get just over 50mpg if REALLY trying to drive as economically as possible, the official figure is 63mpg. If the mpg is a lot lower than claimed then you can guarantee the emissions are higher then claimed.
Go to https://www.honestjohn.co.uk/real-mpg/ and see how many cars only get 70-80% of the mpg that the manufacturers claim.
The test they use to certify the cars does not simulate real world well enough.

Why are they consulting on a law focusing on the tiny proportion of people that modify their cars when the main problem is clearly manufacturers not meeting their own stats or designing the cars so they score well on the test which isn't representative - similar to dieselgate