In particular, her government has resisted an EU Commission demand for tougher limits on Germany's carbon dioxide emissions.

Some of her own political allies and environmentalists wonder what effect this will have when Germany has to try to secure agreement among the 25 member states on an energy action plan with a view to sealing an agreement at a summit in March.

"You need to set a positive example yourself to have any credibility," said Hans-Josef Fell, a Greens party leader on energy issues. "But the government is saying one thing on climate and doing the opposite."

On Jan. 10 the European Commission will set out a series of proposals for energy and environmental policy after 2012, when targets set under the Kyoto Protocol expire.

EU Environment Commissioner Stavros Dimas has already signalled he will push for a 30 percent cut in the bloc's greenhouse gas emissions by 2020.

Merkel, who holds a doctorate in physics and was once German environment minister, said in September she wanted to make cutting emissions of greenhouse gases -- which trap heat in the atmosphere and mostly come from the burning of fossil fuels -- a top priority in her 6-month EU presidency.

But she has gone silent since then as conflicting interests within her cabinet boiled to the surface.

Even Environment Minister Sigmar Gabriel, from the Social Democrats who share power with Merkel's conservatives, has wavered between tough talk on climate change and defending the coal-burning power plants his centre-left party staunchly supports.

For the 2008-12 period, Germany has pressed the European Commission to increase its annual allowance under an EU emissions trading scheme per year to 465 million tonnes of carbon dioxide from 453 million.

Pressure has come from power companies, which rely on highly polluting coal to deliver half the country's electricity.

"When you hear her speeches, Merkel makes it seem like this (tackling climate change) is an important topic for her," Angelika Zahrnt, head of the BUND environmental protection group, told German radio.

"But in the long run, nice speeches aren't going to stop climate change. Only energetic action will make a difference."