"Politicians who let slip the opportunity to save the climate in Copenhagen are in their homes while environmentalists who denounced the lack of summit commitments ... remain in jail without even seeing their families," the coordinator of Greenpeace Spain campaigns, Maria Jose Caballero, said in a statement.

The director of Greenpeace Spain, Juan Lopez de Uralde, and Norwegian Nora Christiasen fooled security staff at the Danish parliament in Copenhagen by drawing up to a December 17 gala dinner of the UN climate conference in a limousine and wearing evening attire.

There, they unfurled banners reading "Politicians Talk, Leaders Act" at the entrance.

Another Greenpeace protester, 37-year-old Swiss national Christian Schmutz Leinhart, who posed as their bodyguard, was also arrested. The fourth suspect, a Dutch Greenpeace activist, Joris Thijssen, was arrested the next day.

Police charged them with illegally entering state property and using false police number plates, and a court ordered them to remain in custody until January 7.

"Greenpeace is waiting to know what will happen after that date," the organisation said in a statement.

It said the four are being held "without trial" with "visits and letters restricted."

Caballero and Uralde's wife, Koro Castellanos, delivered a petition to the Danish embassy in Madrid calling for their release.

Greenpeace said the appeal was backed 50,000 people -- around 30,000 on its website and 20,000 more through social networking sites.

"Denmark is a country where the right to bail until the conclusion of trial is guaranteed, specifically if the act has not posed any threat and has been peaceful," the petition said.

Greenpeace Spain last week condemned the "extreme, unfair and disproportionate" treatment of the four by Danish authorities.

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