France and Germany joined forces yesterday to demand a crackdown on tax havens, amid claims by Nicolas Sarkozy that China could be an obstacle to an ambitious deal.

As aides to Gordon Brown, UK prime minister, worked into the night to find a compromise text on tax havens, Mr Sarkozy hinted that the issue could be the G20 meeting's biggest flashpoint. "The time for pointless summits is behind us," he said.