Czech President Vaclav Klaus said on Wednesday that fighting global warming has turned into a a "religion" that replaced the ideology of communism and threatens to clip basic freedoms.

The right-wing president, a free-market champion, wrote to the U.S. Congress that adopting tough environmental policies to fight climate change would have destructive impact on national economies.

"Communism has been replaced by the threat of an ambitious environmentalism," Klaus wrote in response to questions from the U.S. House of Representatives' Committee on Energy and Commerce.

The U.S. House Subcommittee for Energy and Air Quality was due to hold a hearing on climate on Wednesday with former U.S. Vice-President Al Gore, who sees global warming as a key challenge, and Danish sceptic Bjorn Lomborg, who says governments should focus on fight disease and hunger instead.

Gore, who won an Oscar for 'best documentary' for his "An Inconvenient Truth" movie on climate change, has led a global warming awareness drive in the United States, the world's largest source of gases believed to cause it.

Klaus, who does not hold many executive powers but is by far the most popular politician in the ex-communist Czech Republic, has taken a decisively opposite stance on the issue.

Klaus said poor nations would also be hurt by efforts to impose limits and standards on emissions of gases believed to cause global warming.

"They will not be able to absorb new technological standards required by the anti-greenhouse religion, their products will have difficulty accessing the developed markets, and as a result the gap between them and the developed world will widen," he wrote.

"This ideology preaches earth and nature and under the slogans of their protection -- similarly to the old Marxists -- wants to replace the free and spontaneous evolution of mankind by a sort of central, now global, planning of the whole world," he added.

U.S. President George W. Bush opposes mandatory caps on heat-trapping gases. He pulled the United States out in 2001 of the Kyoto Protocol on global warming, which aims to reduce greenhouse gas emissions.

Klaus wrote that it was futile to fight against phenomena like higher solar activity or the change of ocean currents, and called for avoiding wasting taxpayers money on what he called doubtful projects.

"No government action can stop the world and nature from changing. Therefore, I disagree with plans such as the Kyoto Protocol or similar initiatives, which set arbitrary targets requiring enormous costs without realistic prospects for the success of these measures," he said.