A survey of 1,000 residents from 32 London boroughs found 45 per cent wanted to see a new runway at Gatwick. 39 per cent backed expansion at Heathrow.
According to the YouGov poll the issue of "negative impact on quality of life" of airport expansion was the main concern. Of those surveyed 37 per cent felt Gatwick was best placed to tackle this, while 26 per cent said the same o Heathrow.
The poll findings come as the Government's airports commission conduct a public consultation on expansion before making a recommendation to ministers after the general election.
Gatwick chiefs will fight Heathrow over what it perceives as the weaknesses of its expansion — the environmental impact and the £5.7billion cost to the taxpayer.
Heathrow insists only it can deliver the economic benefits with connections to emerging markets worldwide.
Gatuick Airport CEO Stewart Wingate said: "In this crucial year for the expansion debate, the latest polling is a timely reminder of the growing support and momentum behind Gatwick as the right choice for the UK's next runway.
"From greater competition and more destinations, to lower fares and less noise than Heathrow, the reasons for expanding Gatwick are compelling and numerous."
The poll, conducted online from December 18 to 22, found 49 per cent felt Gatwick was better placed to minimise air traffic over central London compared with 24 per cent for Heathrow.
A Heathrow spokesman said: "Our YouGov polling shows that Heathrow has more support than Gatwick both in London and across the whole of the UK. Furthermore 26 chambers of commerce across the country and the CBI support an additional runway at the UK's only hub airport.
"They recognise the huge economic benefits of Heathrow expansion, almost twice that of Gatwick.
London Heathrow Airport