The action, expected to begin on New Year's Eve, would cause an unprecedented confrontation with the Prime Minister over a project which he has invested with his personal authority.
Mr Monbiot and the This Land Is Ours campaign, for which he is an official spokes- man, dismiss the attempts by Peter Mandelson to head off protests by making the building more environmentally friendly. Last month the Minister without Portfolio dropped plans for a PVC-coated roof after Greenpeace threatened to disrupt construction of the "toxic plastic throw-away monster".
Research by Friends of the Earth has since found that the replacement, Teflon-coated glass-fibre, also poses environmental dangers. And the protesters' objections are primarily at "a total misuse of inner city land - another bonanza for big developers which does nothing for the poor and homeless".This Land Is Ours is calling on its supporters for ideas and energy in its battle against the Dome, telling them: "A delay of just a few weeks would be fatal to this sterile dystopia."
Mr Monbiot said: "The dome sends out a signal that land is a plaything to be used for whatever daft idea developers can come up with, rather than an increasingly scarce resource required to meet people's basic needs. If the Prime Minister is foolish enough to establish this pet project, he should expect to elicit this sort of reaction."
The New Millennium Experience, the company, with Mr Mandelson as its sole shareholder, which is building the dome, said the scheme for the site included housing and was bringing environmental benefits. It was turning land that had been in "derelict and contaminated for more than 20 years" into an area where people could live.
n Evidence of high levels of radioactive waste in the sea less than 10 miles from the Channel Islands is being investigated by the French authorities, writes Geoffrey Lean.
The French police, navy and Greenpeace took samples from around the discharge pipe of the Cap de la Hague reprocessing plant - France's Sellafield. The samples are being analysed. The plant is on the tip of the Normandy peninsula close to Alderney.Reuse content