Brexit could make it harder for the European Union to meet its climate targets, carbon pollution figures show.
A report by the European Environment Agency shows that the UK's greenhouse gas emissions fell by 34.3% between 1990-2014, the biggest percentage drop in the EU apart for eastern countries whose emissions fell sharply when communist-era heavy industries collapsed.
The EU's total emissions would have dropped 22.8% rather than 24.4% during that period if the UK's figures were not included.
Although the EU has already reached its target to reduce emissions by 20% by 2020, in negotiations on a climate deal in Paris last year it pledged to deepen those reductions to at least 40% by 2030.
EU officials have been evasive on how a British decision to leave the bloc would affect its climate targets.
EU climate policy spokeswoman Anna-Kasia Itkonen declined to comment on Tuesday. Last month the EU's chief negotiator in UN climate talks, Elina Bardram, said she was "confident that the British public will vote to remain in the EU".
The report, which was submitted to the UN's climate secretariat, shows Britain's greenhouse gas emissions dropped from 5.67 billion tonnes in 1990 to 4.28 billion tonnes in 2014, in part due to a switch in electricity generation from coal and oil to natural gas and renewable sources. Only Germany had a bigger drop measured in tonnes.
Scientists say man-made emissions of carbon dioxide and other greenhouse gases are causing temperatures to rise, resulting in potentially devastating changes in climate around the world.