A watchdog has warned Transport Secretary Stephen Byers not to break an agreement barring a second runway being built at Gatwick before 2019.
Gatwick Airport Consultative Committee chairman Peter Bryant spoke about his part in the 1979 negotiations which led to the document being signed by West Sussex County Council and the British Airports Authority.
Leaks have suggested Mr Byers will back a second runway when the Government's review into airport capacity is published.
But Mr Bryant said it would take an Act of Parliament to overturn the agreement.
He played a leading role as a senior West Sussex county planning officer in thrashing out the agreement.
The deal was signed with BAA because of alarm sparked by proposals for a second Gatwick terminal.
Local residents believed a second terminal meant another runway.
BAA said a second runway was not in its plans and the agreement was drawn up to remove the issue from the public inquiry.
A Department of Transport spokeswoman branded the leaks "pure speculation".
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