One farmers' union said in some southern areas, where the harvest started in May, the drought had reduced yields so much that the grain was not worth harvesting.

Ministry data put the wheat harvest at 4.75 million tonnes, down 33 percent year-on-year.

Last month the ministry estimated the overall wheat crop at 5.06 million tonnes.

Durum wheat -- grown mainly in the sun-scorched south -- was estimated down 58 percent year-on-year at 1.15 million tonnes. Soft wheat was seen off 18 percent at 3.60 million tonnes.

The barley harvest was now seen at 6.37 million tonnes, down 40 percent year-on-year and below last month's 7.95 million tonnes.

"It could be even worse," said Pablo Resco, a technician at union COAG. "We've had a very dry May, and June is expected to be even drier."

Spain had the driest September-to-March period this year since records started in 1947, and there has been very little rain since then. European traders said on Monday prices were rising because of expected extra demand from Spain.

Like its parched neighbour Portugal, Spain has asked the European Union for drought relief.

The Agriculture Minister has asked the EU for permission to import up to 8 million tonnes of cereals from EU intervention stores, according to a letter seen by Reuters last week.

However, ministry officials say no formal request has been made.

In the letter, the minister said she expected 50 percent of the crop to be lost.