Following the triggering of Article 50 today (29 March), Ingham called on Prime Minister Theresa May to secure a deal with the EU that provides maximum stability for Britain.
Any deal must ensure the UK retains its position as "Europe's most advanced and sophisticated PR and communications market", Ingham argued.
He pointed out that five per cent of UK practitioners are from another EU country, and are not in possession of a UK passport.
"Therefore, if the UK PR industry is to retain and continue to attract talented employees, the status of non-UK citizens must be resolved as a matter of urgency," Ingham said.
"This will be a vital issue for the future of many PR and communications agencies," Ingham said.