Professor Sir David King, the British government's former top scientific adviser, is no stranger to controversy.

He ruffled feathers on both sides of the Atlantic in 2004 when he described climate change as a more serious threat to the world than terrorism.

Earlier this year, he said the Iraq war may come to be seen as the world first’s “resource war”, based on oil rather than weapons of mass destruction.

Now the South African-born academic risks putting more politicians' noses out of joint.

In a speech in Oxford this week, King accused Gordon Brown of talking tough on climate change, but failing to follow his words up with action, mainly due to a lack of public money.

"It is relatively easy, and this is from my direct experience, for a prime minister to make a speech on climate change which sounds very committed, but very much more difficult for a prime minister to persuade the Treasury (finance ministry) to put the finance behind that,” King told the 2009 The Times/Smith School World Forum on Enterprise and the Environment at Keble College, Oxford.

“There is a long distance in government between saying what you think is needed to be said and then doing in terms of making the budgets available.”

Rich nations’ pledges to spend big chunks of their economic stimulus packages on “green projects” have had mixed results, he added.

South Korea has put an estimated 80 percent of its stimulus money into environmental projects, China roughly 50 percent, while the British government is far behind on about 8 percent, King told delegates.

“What happened between Number 10 (Brown’s office) and the decision making process?  I suppose I am going to point at the Treasury,” King said.

The gap between politicians’ fine words and practical action can often be blamed on the government’s reluctance to try to “back winners” with state subsidies.

“That philosophy then blocks the way in the transition between statements from the prime minister and emerging policy,” King said.

Brown would strongly dispute that analysis. In a speech last month, the prime minister compared the challenges posed by climate change to the rebuilding of Europe after World War Two.

He said Britain was at the forefront of the fight against global warming and will support 50 billion pounds of low carbon investment in the current spending period.

King, who is the first director of the Smith School of Enterprise and Environment at the University of Oxford, said he was disappointed by the poor turnout of senior politicians at the World Forum, a three-day conference with many of the world's top climate scientists.

"I tried to pull in a lot of IOUs," he said. "But where was (business secretary) Lord Mandelson, where was (energy and climate change secretary) Ed Miliband, where was (opposition Conservative leader) David Cameron?"