He said the council had engaged a private investigator from LKA Group, which describes itself as “Australia's leading national provider of investigative services”.

The leaked documents related to a proposal at Waterloo Point in Swansea for a 200-berth marina, with 20 floating houses and a residential development.

Councillor Kent said a deputation about the marina was heard by the council in September.

“Essentially it was private and confidential within council and council had discussed it at length,” he said.

“A lot of what we try and do with developers is have the discussions to see whether there are opportunities, and then if there is you mould those into opportunities that will eventually come off.

“So you keep working with the developers to see whether they are prepared at the end of the day to put their money up and a lot of that stuff is commercial-in-confidence and that is the problem.”

The council has been conducting an internal investigation since September, and Councillor Kent described the situation as a “difficult one”. He confirmed that a police officer had been asked to witness statutory declarations made by councillors and staff.

“The council wanted someone independent to do that and obviously I am a JP and all of that business, but I felt I should step aside and get someone else to do that,” he said.

He said the costs involved with hiring the private eye would be revealed at the end of the investigation. Local Government Minister Peter Gutwein said he had been made aware of the situation.

“The Glamorgan Spring Bay council have taken some steps to try to get to the bottom of it but at this stage the Local Government Division isn’t conducting a formal inquiry,” Mr Gutwein said.