The government's chief scientific adviser has told the Independent that he is being aggressively targeted by American lobbyists trying to discredit his view that man-made pollution is behind global warming.

Sir David King said he was being followed around the world by people who want to cast doubt on the science of climate change.

"They'll be in the audience to stand up and raise questions to get into the audience's mind that I haven't represented a balanced view," he said.

"You have a group of lobbyists, some of whom are chasing me around the planet, which I'm chuffed about because it means they are worrying about what I'm saying, and these lobbyists stand up after I've given an hour's talk and say, 'There are scientists who disagree with you'," Sir David said.

"I always say, 'Which bit of the science that I've just presented to you are you challenging'? I don't get the answer."