With double-digit scores across Europe's biggest countries including a stunning 20 percent in Germany, the Greens bagged record gains in EU elections on Sunday with younger voters leading calls for action to halt global warming.

The environmental party doubled its score in Germany from the last EU elections in 2014, knocking the Social Democrats out of their traditional second place.

The amazing gains continued in France where the Greens were number three with 12 percent, while in Austria, Ireland and the Netherlands, they garnered double-digits.

In Britain, they were on 12.4 percent, nearly double their previous score, and beating the ruling Conservatives into fifth place.

"To see The Green Party beating the Conservatives so far in these elections is truly amazing. Something seismic is happening in British and European politics," said Alexandra Phillips, Green Party candidate for Southeast England.