In its first report, the Committee on Climate Change will weigh how Britain can meet ambitious goals to slash planet-warming greenhouse gas emissions while taking account of the economic downturn, energy security and volatile fuel prices.

British Prime Minister Gordon Brown set up the committee to advise ministers on what his government describes as the world's greatest environmental challenge.

Britain and other countries say climate change will cause extreme weather, leading to food and water shortages, rising sea levels and flooding and outbreaks of disease.

Energy and Climate Minister Ed Miliband has already accepted the committee's proposal to sharpen a binding national target to cut greenhouse gas emissions by 2050, to an 80 percent cut from 60 percent.

Now the committee chaired by Adair Turner -- also head of Britain's financial watchdog -- has the job of advising how the government can achieve this, possibly recommending the end of unconstrained emissions from coal plants.

Coal is one of the world's cheapest and most accessible forms of energy, but also one of the main contributors to climate change.

The committee will advise on constraints on new coal-fired power plants which may include attaching expensive carbon-cutting technologies which would dramatically dent coal's competitiveness.

German utility E.ON AG plans to build a new coal plant in Kingsnorth in Kent, in south-east Britain. Climate protestors scaled the security fences in August in an attempt to disrupt output at an existing plant there, due to close by 2015.

The government wants any new coal plants to demonstrate plans for fitting, in the future, technology called carbon capture and storage (CCS) which traps carbon dioxide (CO2) emissions and buries them underground.

The committee may set a clear date for when CCS should become mandatory on such new build coal plants.

Utilities say fitting CCS will cost around $1 billion extra per plant and cut efficiency by about one quarter.

They are also concerned that there will be a power generation gap between 2015 and 2020 which will have to be filled by gas-fired plants, because there is too much uncertainty in the government's stance on coal.

"Government policy towards coal needs to be clearer and firmer before people will go ahead," said David Porter, chief executive of the Association of Electricity Producers.

Turner's group is also expected to advise how achievable is Britain's target to get 15 percent of its energy from renewable sources by 2020 versus 1.3 percent in 2005.

Investors in renewable energy like wind and solar power hope that if the report's proposals are implemented by the government, there will be more clarity.

"Broadly speaking it ought to be welcome to investors because it should set a playing field against which investments can start to be made with a medium-term perspective," said Ian Simm, chief executive of Impax Asset Management.

The report comes as 190 countries meet in Poznan, Poland, in December 1-12 talks to review progress in a two-year drive to agree a new global climate treaty by the end of 2009.