Passing through London on her way to the Group of Seven meeting of finance ministers and central bank governors in Marseille, she called on countries to “act now and act boldly to steer their economies through this dangerous new phase of the recovery”.

“The key is for policymakers to act with conviction and urgency in tackling today’s challenges, while at the same time being nimble, should circumstances change,” she said.

Displaying the same lack of confidence in the global recovery as the Organisation for Economic Cooperation and Development on Thursday, Ms Lagarde said that “the necessary handoff from public to private demand is not taking place”.

Although she was seeking to drive the G7 towards concrete action and away from a mood of resignation, the political difficulties of the task were laid bare by a lack of specific recommendations of new policies that politicians should adopt. The path for fiscal consolidation, she said, should differ according to the circumstances of each country.

She praised president Obama’s jobs speech for its balance between supporting growth in the short term and the longer-term ambition to cut the deficit and debt. She agreed with George Osborne, the UK chancellor, that its rapid deficit reduction was “essential to restore debt sustainability", but she also repeated the IMF’s call on the UK authorities to be nimble.

Rather than calling on the eurozone to do more, she urged European governments to implement the agreements underpinning the second Greek loan package as soon as possible, while repeating her earlier calls for more capital to be injected into the European banking system.

Given the political difficulties of telling her shareholder governments what to do, Ms Lagarde’s ambitions for central banks and monetary policy were more concrete.

“Policymakers should stand ready, as needed, to take more action to support the recovery—including through unconventional measures,” she said, specifically singling out the Bank of England as having room for more action if the recovery does not improve.

There is little expectation of firm agreements at the G7 meeting on Friday, with the event being seen more as a stepping stone to other international economic meetings later this month, in October and in November.