The claims are made in a submission to the Airports Commission, in which Gatwick says if Heathrow expands, airports across the UK will lose their ability to compete and grow.
It also says competition between airports has been one of the great successes of recent UK aviation policy and has helped 'drive airfares down and improve consumer choice'.
The latest submission, adds Manchester, Edinburgh, Newcastle and Birmingham are also increasingly able to offer passengers affordable direct flights to international destinations across the world.
Gatwick says the trend is likely to continue as the next generation of fuel efficient aircraft - make direct flights to destinations further afield increasingly viable from non-London airports.
CEO Stewart Wingate, explains: “Competition between the UK’s airports has been one of the great successes of recent industrial policy and has delivered more choice, better standards and lower airfares for consumers. Why wouldn’t you want that trend to continue?
“A new runway at Heathrow would give the airport too much market power. However if Gatwick built a second runway it could compete more vigorously with two runway Heathrow, which would deliver benefits for both consumers and other UK airports.”
Gatwick adds that a third runway at Heathrow would threaten the commercial viability of other UK airports by reducing choice and giving Heathrow too much market power, but development at Gatwick would generate more rigorous competition among airports in London and South East England and would help other UK airports to compete, specialise and grow.
The submission was in response to the Airports Commission’s call for evidence on the connectivity and business models of the UK’s existing airport capacity, and was backed up by Birmingham Airport.
CEO Paul Kehoe, says: "We need a network of national airports across the country, with healthy competition driving up standards and choice for passengers.
"Long-haul airports across the country, like Birmingham, play a central role in providing this choice, and the global connectivity we deliver is essential for supporting the growth of our regions. This would be threatened if we were to allow one single hub to dominate the market.”