Pierre Condamin-Gerbier, a key witness in a major French tax fraud investigation, is under arrest in Switzerland after breaching the country's banking secrecy laws by testifying in the investigation into France's former budget minister Jerome Cahuzac.
But Condamin-Gerbier's lawyer told Swiss financial daily Agefi the former banker had invented a list of French politicians with secret Swiss accounts.
"This list never existed," lawyer Edmond de Braun said, adding that his client had lied "to silence the threats that he was subject to at the time."
The former banker "now acknowledges that this was a very clumsy" strategy, he told Agefi.
He quit over an undeclared foreign bank account said to contain around 600,000 euros ($770,000).
Condamin-Gerbier, who remains in Swiss custody, told media he had given French investigators details of 15 French politicians and "big names" with undeclared bank accounts in Switzerland.
De Braun told Agefi his client became entangled in the affair after French daily Le Monde published a "defamatory" article about him.
"He wanted to correct what had been said about him through other media, and lost himself in this inextricable process. It was the worst thing he could have done," de Braun said.
Condamin-Gerbier's former employer Swiss bank Reyl and Cie, which is at the heart of the Cahuzac scandal and which is under investigation in France for enabling tax fraud, filed a criminal complaint against its former employee in June for among other things "falsifying documents and violating professional and commercial confidentiality."