Europe's wine production has dropped to levels unseen since World War II after extreme weather battered top producers Italy, France, Spain and Germany, according to the main farmers' union.

Copa-Cogeca said quality was high and prices will rise but not enough to compensate producers for losses as drought and frosts linked to climate change damaged grapes.

Total wine production across the European Union is an estimated 145 million hectolitres for 2017, down about 14% from last year's levels, the union said.

"This year our vineyards have been badly affected by the impact of climate change and extreme weather events ranging from frost to drought," Copa-Cogeca executive Thierry Coste said.

Many producers harvested grapes two weeks early on average, he said.

"The quality of the grape is nevertheless expected to be very good across Europe which should make for an excellent wine," Mr Coste added.

A vineyard partially destroyed after a hailstorm near the southern French city of Montpellier

The union did not provide details of the previous lowest output but a spokeswoman said it was the lowest since World War II as Italy, France, Spain and Germany all saw sharp declines.

Italy's production fell to 40 million hectolitres, down about 26%, while France's output fell to around 37 million hectolitres, about 18% below last year.

Italy's annual wine harvest got off to its earliest start in a decade following months of drought

Experts already predicted in August that France would suffer its poorest wine harvest since 1945 after an unusually mild March and frosty April, although a hot summer would deliver top vintages.

The 2016 harvest was already one of the poorest in 30 years.

Spain's output dropped to an estimated 36 million hectolitres, down 20% from 2016, Copa-Cogega said.

Germany is estimated at 7.5 million hectolitres, down from about 8.5 million hectolitres last year.

Wine output in the four leading producers also declined in 2016 from 2015, though by a smaller amount.