Rightmove is also seeing evidence that house price growth in London is no longer being driven by the wealthy "prime central" boroughs.
London's worst-performing borough in March was named as Kensington and Chelsea, where asking prices had dropped by 2.4% on the previous month.
But the average price tag for a home in the borough was still £2.1 million.
The English capital's best-performing borough was found to be Haringey, where prices had surged by 9.5% month-on-month to reach £597,634 typically.
Westminster and Camden, where average asking prices were above £1 million, were also among Rightmove's worst-performing areas in London in March, while Barnet and Hounslow, where prices were around £600,000-plus, were among the best.
Luke Hanrahan has been investigating what's behind London's housing shortage and the impact it's having on those who live here.
The mayor believes the economic recovery should force developers to rethink their commitment to social housing.
The jury is still out on the Help to Buy scheme, designed to help people take their first steps on the property ladder.