But it does not set EU-wide sanctions to the dismay of environmentalists who doubt it will have much impact.

"It is not as strong as we would have like to see it ... it does not lead to the harmonisation of criminal law that would have helped prevent environment crimes," said Regina Schneider, from the European Environmental Bureau, a federation of more than 140 non-governmental environmental organisations.

"It is first step in right direction but no more," she said.

EU ambassadors are set to give the final green light to the text on Wednesday, EU officials said, on the same day as the European Parliament is scheduled to vote on it, after backing it in a parliamentary debate on Monday.

The European Commission had originally proposed at least sentences of between 5 and 10 years in jail for environmental crimes that killed or seriously injured people, and fines of more than 1 million euros ($1.6 million) for companies involved.

It would have been the first time that EU-wide minimum sentences, which already exist for terrorism and drugs trafficking, were applied to environmental crimes.

But the bloc's top court ruled at the end of last year that the EU could not specify the type and level of sanctions, EU Commissioner Jacques Barrot and lawmakers said on Monday.

The text now only mentions "effective, proportionate and dissuasive criminal penalties," with no details, something environment groups say will weaken its impact.

Barrot and senior EU lawmakers said during a parliamentary debate on Monday the law would have a deterrent effect.

"It still is a big step forward for environmental protection," EU lawmaker Dan Jorgensen said on behalf of the assembly's environment committee. "The big problem of EU environment policy is that it is not applied in EU countries... this is what we may have well solved with this."