The government has failed to stand up to President Bush over climate change, the former head of the Met Office has claimed.

Sir John Houghton accused the prime minister of refusing to take up the issue in order to avoid upsetting Washington.

"Britain, presumably because Blair wishes not to offend George Bush, is falling behind too," he claimed.

Writing in the Guardian, Houghton warned global warming is as great a threat to the world as weapons of mass destruction.

"The parallels between global climate change and global terrorism are becoming increasingly obvious," he warned.

Houghton, who is a member of the UN panel on climate change, said the rising number of tornados and heat waves that have killed hundreds are likely to become more frequent.

He called on the government to challenge the US government, which has been reluctant to back environmental treaties such as the Kyoto Agreement, because the US is the world's biggest polluter.

Houghton urged Blair to use his political influence to pull together a "coalition of the willing".

"History might not only 'forgive' him, but also endorse Britain's contribution to long-term global security," he wrote.