PRWeek understands that Smith’s consultancy Incorporated London has been hired to push the expansion agenda by Gatwick, which has existing relationships with Fishburn and London Communications Agency.
The appointment comes as the Airport Commission studies a range of options to increase aviation capacity in the south of England.
Last month, the airport published more details of its proposed £7bn second runway and launched a campaign called Gatwick Obviously. It claimed that the airport's expansion would have an "Olympic-scale effect" on south London.
Smith, who is understood to have been hired within the past three months, has extensive Whitehall experience including acting as Prime Ministerial spokesman for Blair and leading communications on the delivery of the Olympics.
One agency source praised Smith as "someone with first-class contacts across the spectrum and a very good understanding of how government works".
However, they added that with another runway at Heathrow among the options being considered by the Airport Commission, Gatwick had a tough challenge on its hands.
"Gatwick wins on a number of criteria against Heathrow, but does it have the credibility among the business community and airlines? They need them to come out and say it has more potential than Heathrow."
A spokesman for Gatwick Airport said: "London Gatwick is the obvious choice for the next runway and has built the best possible team to support its campaign."
Earlier this year, PRWeek revealed that the airport was set to review its digital and consumer agencies.
Incorporated London declined to comment on the hire.