Four Greenpeace activists today scaled the Treasury building to ask Chancellor George Osborne to provide a "green bank".
The environmental campaigners said such a move could provide tens of thousands of new jobs.
The organisation said four of its members climbed on to the building in Westminster at 6am and were preparing to unfurl a banner reading: "Remember George, Green bank = New jobs".
One of the activists, Emma Gibson, 41, said: "We are going to unfurl a giant note to the Chancellor, asking him to invest in a green bank, because it's going to create tens of thousands of green jobs, in the Comprehensive Spending Review.
"It's something George Osborne and other ministers have talked about, where the Government puts in an amount of money which can only be spent on green projects, which encourages private investors to match it.
"It could do a lot for economic recovery."
Scotland Yard confirmed that four protesters were on the second floor of the building.
"Cordons are in place and we are observing the scene," a spokesman said.Reuse content