They're not, really, though.
Only the very smallest diesels will turn in 104g/km of CO2.
Just checked one of the close, diesel, opposition - Golf 2.0TDI 110.
128g/km.Even a 'Bluemotion' comes in at 122g/km.
The very best of the diesel competition is the 118d with 119g/km.
This year's new Prius will be under 100g/km and qualify for free VED.
Yes, but the biggest car that's in is the Corsa, which is significantly smaller.
Much as I hate to admit it, the Prius makes a lot of sense for many people - a big 5 door hatch with the VED and company car tax of a supermini.