The MEPs amended proposals to reduce emissions from light commercial vehicles by lowering the 2020 emissions limit to 140 grammes per kilometre. The European Commission had aimed to set the limit at 135g/km.
The committee supported the EU executive's plans to phase in a 2016 target of 175g/km.
The new legislation is designed to reinforce the EU's efforts to halt its rising transport emissions after similar emission performance standards were set for passenger cars in 2009. Light commercial vehicles, used mainly by businesses, make up around 12% of the fleet.
MEPs also voted for weaker penalties, which the Greens attributed to a push from centre-right MEPs. Manufacturers would therefore pay a fine of €95 per gram of CO2 per vehicle exceeding the emissions limit by 2019, instead of €120 as proposed by the Commission, in line with penalties agreed for car manufacturers in 2008.
The majority of the MEPs sitting in the committee took the view that the van industry's dire economic situation and long production cycles merit more carrot and less stick. It extended so-called "super credits," which allow manufacturers to continue selling gas-guzzling vans if they are compensate for them with highly efficient vehicles, such as electric vans.
Environmentalists criticised the committee for further diluting what they saw as an already weak proposal from the EU executive, pointing out that some top-selling van models have already reduced their CO2 emissions by more than 10% since 2007. The Commission's proposal would only require manufacturers to cut emissions by 14% between 2007 and 2016, said Greenpeace.
The Parliament's industry and transport committees had previously recommended introducing speed limits for vans as a way of reducing their emissions, but these were scrapped from the draft position.
The committee's proposal was passed narrowly with 32 votes in favour, 25 against and one abstention. It will be put to a vote before the plenary in November, after which EU member states will have to come forward with their first position on the legislation.