The bill to revive ailing environments - which aims to restore nature on 20% of EU land and sea - is facing a political backlash from the European People's Party group in the EU Parliament, which has called for its rejection.
In a tight vote, 44 lawmakers voted for the law and 44 against, meaning it failed to win majority support.
The bill now heads to a full EU Parliament vote on July 11, where failure to win majority support would kill off the proposal.
Supporters from other parliament groups said they would try to club together to find a compromise deal ahead of the full parliament vote.
Despite that, EU countries agreed a position on the nature bill last week - weakening some targets and asking for more EU money to support farmers in restoring nature, but backing its overall aims.
Persons:
Anne Sander, Cesar Luena, parliament's, Kate Abnett, Bart Meijer, Frank Jack Daniel, Conor Humphries
Organizations:
REUTERS, Union, European People's Party, European Commission, EPP, Thomson
Locations:
Hymettus, Athens, Greece, BRUSSELS, Brussels, Ireland, Belgium