Ministers have been accused of inadequate and inconsistent leadership over green issues in a strongly-worded attack by a leading environmentalist.
Sir Jonathon Porritt said "soaring" speeches about making the UK a world leader in fighting climate change were not backed up by action.
He said policies in the pre-Budget statement were "crabby incrementalism".
The government said the measures - also criticised by environmental groups - were an "important step forward".
A Defra spokeswoman said they built on existing policies and programmes.
"The £1.1bn environmental transformation fund, which will help to develop and roll out low carbon technologies in the UK and in developing countries, is a particularly significant investment," she added.
"This is by no means the end of the government's efforts to fight climate change, and we will continue to push towards a low carbon economy through a variety of fiscal, regulatory and voluntary approaches."
'Incredibly inconsistent'
Sir Jonathon - who chairs the government-backed Sustainable Development Commission - told BBC Radio 4's Today programme tougher financial decisions were needed to effect real change.
"What we are seeing at the moment is such a woeful falling short of what could be done that we are really nowhere near the pain barrier," he said.
"Our biggest worry at the moment is that this leadership is incredibly inconsistent."
Chancellor Alistair Darling announced a modest annual cash rise for the Department for Environment, Food and Rural Affairs, a switch in air passenger duty to encourage more fuel-efficient aviation, and cash for an environmental transformation fund to drive green technology at home and abroad.
Prime Minister Gordon Brown pledged at last month's Labour conference to "make Britain a world leader in tackling climate change".
Global debates
Sir Jonathon said that "within a few days of a speech like that you have an opportunity to demonstrate leadership in the world which ends up with yet another manifestation of what I think has to be described as crabby incrementalism to be honest.
"Just a little bit here, a little bit there, without actually sending a signal to citizens in the UK that this is indeed now the most serious problem that we have to deal with and we have to use the tax and expenditure systems in this country to address it."
He added: "If the UK is going to have any impact in these global international debates, we have to be able to demonstrate here in our own backyard what it looks like to move cost-effectively towards a low-carbon economy."
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