Khan has the support of 32 per cent of voters, according to YouGov, while Goldsmith trails with 25 per cent of the vote. Both front-runners increased their share of the vote by one per cent since YouGov last polled voters in January.
Khan's lead increases to nine points, however, when pollsters exclude people who say they don't know how they would vote or don't intend to vote in the elections this May.
Nearly one in four Londoners remain undecided of how they will vote, according to YouGov.
Among the smaller parties, Ukip candidate Peter Whittle has the backing of four per cent of voters, while Green Party candidate Sian Berry commands three per cent of the vote. Liberal Democrat candidate Caroline Pidgeon and Respect candidate George Galloway both polled with two per cent of the vote.