London is now the world leader in wireless deployment, according to the sixth annual RSA wireless survey.

The number of wireless broadband networks in the capital increased from 2,747 in 2006 to 7,130 in 2007. The rate of growth is also speeding up, swelling by 160 per cent compared to last year.

"This stellar growth has really been driven by business," said Tim Pickard, vice president of international marketing at RSA.

"We were significantly behind New York last year, so this result is remarkable. It is a technology that businesses want to adopt."

This year's survey covered New York, Paris and London and found the French lagging badly in Wi-Fi deployment. The country has just 825 hotspots compared to 6,371 in New York.

But the report also found large numbers of unsecured networks in all three cities. One in five London networks was wide open which, while an improvement on last year when the figure was over a quarter, is still a significant safety risk.

Also worrying was the increasing number of networks using default passwords. Thirty per cent of wireless access points were using defaults, up from 22 per cent last year.