New carbon pollution figures show the European Union may find it harder to meet its climate targets if British voters decide to leave the bloc in a referendum this week.

A report Tuesday by the European Environment Agency shows that Britain's greenhouse gas emissions fell by 34.3 percent in 1990-2014, the biggest percentage drop in the EU except for eastern countries whose emissions fell sharply when communist-era heavy industries collapsed.

If it weren't for Britain, the EU's total emissions would have dropped 22.8 percent rather than 24.4 percent during that period.

Although the EU has already reached its target to reduce emissions by 20 percent by 2020, in negotiations on a climate deal in Paris last year it pledged to deepen those reductions to at least 40 percent 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 U.N. climate talks, Elina Bardram, answered by saying she was "confident that the British public will vote to remain in the EU."

The report, which was submitted to the U.N.'s climate secretariat, shows Britain's greenhouse gas emissions dropped from 5.67 billion tons in 1990 to 4.28 billion tons 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 tons.

Scientists say man-made emissions of carbon dioxide and other greenhouse gases are causing temperatures to rise, resulting in potentially devastating shifts in climate around the world.