"We can expect electricity shortages when the temperature falls," said Lars-Erik Axelsson from SKGS, an organisation representing energy-intensive sectors such as the forest industry.

Pro-nuclear lobbyists also say that Sweden is more and more dependent on imported energy, much of it generating greenhouse gases, at a time when its hydropower reservoirs are low.

The Social Democrat government, whose voters are split over nuclear power, is expected to decide in February or March on whether to close down the second of two reactors at the Barseback power station at the southernmost tip of Sweden.

The first reactor was closed down in 1999, in line with a referendum almost 20 years earlier that Sweden, like Germany, would gradually close its nuclear plants.

TO SHUT OR NOT

"We think that Barseback 2 cannot be closed down and Barseback 1 should be reopened," Axelsson said.

On Tuesday, representatives of big industry trade unions, which traditionally support the Social Democrats, also demanded that Barseback 1 should be reopened.

The Barseback plant is part of energy group Ringhals AB, which is 74 percent owned by state power company Vattenfall AB

and 26 percent by a unit of Sydkraft AB. Sydkraft is controlled by Germany's E.ON Energie (EONG.DE).

So far the government has not set a firm timetable for closure of other plants, which together generate almost half of Sweden's electricity, because there are no alternative renewable power sources in place.

Barseback 2, a 600 megawatt facility, has drawn harsh criticism from neighbouring Denmark. The plant lies a mere 10 kilometres (6.2 miles) from Copenhagen, which itself has no nuclear power plants and exports coal-based energy to Sweden.

Some Social Democrats politicians have vowed the plant will be closed down this year, but critics say that is unlikely. Trade and Industry Ministry Leif Pagrotsky declined to comment.

Ake Rangborg, spokesman for energy lobby Svensk Energi, said he was certain parliament - which has the final say in the matter - would prolong Barseback 2's lifetime.

"It would be nearly political suicide not to do it after this winter," he said.

Electricity spot prices on the Nordic power exchange Nord Pool have soared after a dry summer and autumn which left the region's water reservoirs at their lowest levels in decades.

But Joran Hagglund, party secretary of the Centre Party which is in the opposition but backs plans to phase out nuclear power, said the current situation also had its bright spots.