The proposal is the latest push by the European Parliament to clamp down on greenwashing, following the final adoption last month of a law banning broad, generic claims such as labelling products "eco-friendly" or "natural".

Now, lawmakers want to go further by mandating that specific environmental claims be subject to systematic verification, with the onus on companies to provide evidence ahead of time.

Lawmakers voted by 467 to 65, with 74 abstaining, in support of the new "Green Claims Directive," which will now be put forward for negotiation among the EU's 27 member states.

The text's backers highlighted that of 150 green advertising and labelling claims examined by Brussels, more than 50 percent were found to be "vague, misleading or unfounded."

This was true across all sectors -- from textiles to cosmetics to household goods. Forty percent of claims were found to have no factual basis at all.

Likewise, half of around 230 ecological labels examined were based on weak or non-existent checks.

"Consumers and entrepreneurs deserve transparency, legal clarity and equal conditions of competition," which don't exist if some companies are "cheating", said parliament rapporteur Andrus Ansip.

The new rules would force companies to submit evidence before marketing products as "biodegradable", "less polluting", "water saving" or having "bio based content".

Member states would assign verifiers to pre-approve claims -- a process that should take 30 days or less in "simpler" cases -- with very small companies exempt.

Environmental certification systems would be subject to the same rules -- with the exception of the EU's official "Ecolabel".

Failure to comply would trigger penalties including exclusion from procurement processes and fines of at least four percent of annual turnover.

"Consumers are paying more and more attention to the environmental impact of what they buy, and yet more than half of products carry vague, misleading or baseless green claims," said Pascal Canfin, chair of the European Parliament's environment committee.

"With this new directive we are saying time's up," he said. "Protecting the environment cannot be treated like a game."

The legislation would uphold a prior EU ban on companies invoking carbon offsetting to allege that a product is beneficial or neutral for the environment.

Companies would be allowed to mention carbon offsetting and removal only if they have already reduced their emissions as much as possible and use the schemes for residual emissions only.