SW MEP Caroline Voaden voted this week to block legislation that would have weakened EU rules protecting bee colonies from toxic pesticides.
The European parliament vetoed the move by member states and the European commission on Wednesday.
Caroline said: "I'm proud to have signed this objection in my group, and supported this vote in the European Parliament. It's exactly the sort of work we need to do - and can do - in this chamber."
MEPs blocked revised legislation that was said to ignore the risk to bee larvae from long-term exposure to chemicals, known as chronic toxicity.
The MEPs instead argued a guidance document (pdf) produced by the European Food Safety Authority (EFSA) in 2013 should be fully implemented.
The guidance seeks both to protect bees from adverse effects from a single exposure or multiple exposures over a short period of time, known as acute toxicity, and also long-term exposure.
Sixteen member states, which have not been publicly named, lobbied against the full implementation of the guidance before the new rules are brought to a vote in the European parliament.
MEPs who led the way on the parliamentary veto claimed the new generation of systemic pesticides, which are applied via seed treatment rather than spraying, made chronic exposure particularly relevant.
Bee populations have collapsed around the world and the use of pesticides is said to be the main cause.
A 2019 analysis of 353 wild bee and hoverfly species in the UK found the insects have been lost from a quarter of the places in which they were found in 1980.
The parliamentary veto was passed by 533 MEPs, with 67 voting against and 100 abstentions.
Read the full Guardian story here.