Environmentalists have welcomed the Government's decision not to block efforts to ban polluting "tar sands" from Europe, as a vote on the issue ended in deadlock.

The UK was among the EU countries whose officials abstained in a key Brussels vote over moves that would effectively stop the use of unconventional oil, extracted in Alberta, Canada, as a transport fuel in the bloc.

Green groups had feared the coalition would bow to lobbying by the Canadian government and oil companies and vote against efforts to ban the fuel.

As a result of the abstentions, there was no majority for or against the move and it will now be decided on by EU ministers in June - which campaigners hope will make the process more transparent.

The European Commission has proposed to rule tar sands as more polluting than conventional transport fuels under the Fuel Quality Directive, which commits the bloc to cutting emissions from the production of transport fuel used in Europe by 6% by 2020. The move could effectively ban the use of oil from tar sands in Europe if the bloc is to meet the directive's target.

If tar sands, which produce more emissions than conventional oil due to the energy required to extract them, are fully exploited it will be "game over" for the climate, campaigners have warned.

Following the vote, senior policy adviser Joss Garman said the decision by Lib Dem transport minister Norman Baker to instruct officials to abstain, rather than vote against the commission's proposals, showed the Lib Dems were maintaining their opposition to tar sands.

The adviser said: "Norman Baker should be congratulated. It's obvious that he's reacted positively to pressure from the clean energy lobby, but the Government now needs to go further. Today's abstention helped prevent a victory for an industry that produces the dirtiest oil on Earth but if we're going to keep tar sands out of Europe we now need Nick Clegg to step in and ensure that when ministers meet in June the result is a European ban on tar sands."

Nusa Urbancic, of environmental group Transport & Environment, said: "It's good to see this decision being brought out into the open. The behind-closed-doors process for implementing the law has enabled vested interests, particularly countries and oil companies with major tar sand investments, to hold up progress. It's now time for every EU country to show its hand: do you want a cleaner transport energy future or not?"

Friends of the Earth urged the Government to stop "sitting on the fence" on tar sands. The environmental group's energy campaigner Tony Bosworth said: "Tar sands oil is one of the dirtiest transport fuels - EU ministers must vote to keep them out of Europe or our ability to tackle climate change will be undermined. The UK Government must stop sitting on the fence on this issue."