Greenpeace protesters have climbed the Treasury building in Westminster to call for a "green bank" to be set up.
Four campaigners scaled the building at 0600 BST on Tuesday, unfurling a banner addressing Chancellor of the Exchequer George Osborne.
It said: "Remember George, Green bank = New jobs."
The Metropolitan Police said the four climbers were still on the building. A spokesman said: "Cordons are in place and we are observing the scene."
The stunt came as Mr Osborne prepares to unveil the government's Spending Review.
Before scaling the building, one of the protesters, 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.
"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."