Lawyer Sutha Prateep Na Thalang, a member of the Chalong Bay Preservation Group, said Phuket's coast was governed by a variety of bodies with different powers and little coordination.
The Marine 5 office controlled the beaches but was unable to enforce regulations, he said.
''If you stay in a forest the Forest Department takes care,'' he said. ''If you stay in a national park the National Parks department takes care.
''But local councils look after the beaches and they do not have the power of enforcement,'' he said.
Phuket had grown without planning, he said.
As a result, opportunism had taken hold, Khun Sutha told a gathering of about 300 people at a seminar on Phuket's coastal issues at Prince of Songkhla University.
He said piers were for the public but marinas were for private use and their development contravened the principle of keeping the entire coast available to the public.