But now the government is hinting that the plants, which provide a fifth of Spain's electricity, could have their working lives extended.

"We haven't drawn up a calendar for closures because we have to decide whether we are in a position to close them or not," Soraya Rodriguez, the Socialist party's environment secretary, told Reuters in an interview late on Tuesday.

"At the moment the government is not in a position to do it because we do not have the renewable alternatives available."

Soaring oil prices and the need to curb carbon dioxide emissions have reopened the nuclear debate in several countries and Spain's supposedly anti-nuclear government is being careful to keep its options open.

The party's policy is unchanged, Rodriguez said, but there would be no decisions on closures before the next general election, due by March 2008.

One small plant with a history of technical problems, closed in April this year and the next oldest -- also relatively small -- is due to start a two year review this year to determine whether it can operate after its licence expires in 2009.

The seven big reactors, which each have capacity of around 1,000 MW, were inaugurated between 1983 and 1988. Most now have licences to operate at least until 2010.

Rodriguez said the government was under no pressure now to rule on extending the life of nuclear plants and implied that, although it has the last word, it would take a back seat in the process.

"The Nuclear Safety Council will make its recommendations on whether they can be prolonged and then the owners will decide if that is profitable," she said.