Port producers say the damage suffered by their vineyards in recent hailstorms is not as bad as first feared - but is still the worst in living memory.

About 10-20% of the Douro Valley's crop was destroyed in the violent but localised hailstorms which hit the valley on 14 June. Hailstones averaging 1cm in diameter fell, with total precipitation of 80mm in one hour.

Worst affected were vineyards in the Pinhão and Rio Torto valleys, important to the production of premium Ports and including many famous quintas such as Noval, Cavadinha and Roêda.

Adrian Bridge, managing director of The Fladgate Partnership, said that about 750,000 out of the group's 1.3m vines had suffered damage, but added that crop reduction might only be 40% with the growth of secondary shoots.

The Portuguese Ministry of Agriculture is supplying free sprayable calcium to farmers to help vines recover, and is considering the issue of compensation.