The government came under fire on Monday for not doing enough to protect the environment.
Greenpeace activists blockaded three entrances to the Prime Minister's home with massive mounds of coal.
And environmental charity WWF UK said the UK has wasted opportunities to do more with its presidency of the EU and the G8 group of wealthy nations.
But a Downing Street spokesman said the government had made good progress in the G8 on tackling greenhouse gases.
A truck bearing the slogan 'Blair - Climate Failure' dumped several tonnes of coal across three entrances to Downing Street.
Another, heading for the Whitehall entrance, was stopped by police.
Greenhouse gas
Greenpeace says Mr Blair is not fulfilling his commitment to the Kyoto Protocol - an international legally binding agreement to reduce greenhouse gas emissions worldwide.
Spokesman Stephen Tindale said: "We've blockaded Downing Street with coal because Tony Blair has failed on climate change."
But the government's chief scientific advisor Sir David King said the UK's presidency of the EU and the G8 had achieved "an enormous amount".