Scotland Yard confirmed Bridgewater was arrested by the Economic and Specialist Crime Directorate of the Metropolitan Police on 23 May, after it received a complaint following the agency's annual auditing process.
Bridgewater and a man in his 30s were taken to an Essex police station and were bailed to return in September.
Hicklin Slade's clients include Camelot and Honda. Both pledged to continue to work with the agency.
Bridgewater left Hicklin Slade in December 2004. In a statement, the agency said: 'During recent routine internal audit processes, certain irregularities were found. Following an investigation, a report was made to the police.'
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