MEPs narrowly failed to overturn the decision to weaken diesel emission limits today, with 317 voting in favour of the rejection, 323 against and 61 abstaining.
Under an EU agreement reached by national governments including the UK in October last year, diesel cars will be allowed to spew out double the current legal limit of deadly nitrogen oxides (NOx) pollution in order to be able to meet new stricter tests coming into force from 2017.
The European Commission has committed to holding an annual review of these rules from next year and to gradually reduce the extent to which diesel cars can pollute above the legal limit.
Liberal Democrat MEP Catherine Bearder, a lead negotiator on the EU's new air quality law, commented:
"Today was a good day for dirty deals and a bad day for cleaner air.
"But the close vote shows there remains strong opposition to the weakening of diesel pollution limits.
"The Commission must now live up to its word and tighten up emission limits as soon as possible.
"Carmakers can and must do more to cut the deadly pollution plaguing our cities."