A key witness in the investigation against France's former budget minister Jerome Cahuzac has been arrested by Swiss authorities, the Swiss prosecutor's office confirmed on Saturday.
Swiss newspaper Tribune de Geneve reported that Pierre Condamin-Gerbier was arrested shortly after returning from France, where he had been a witness before a parliamentary commission investigation into alleged tax fraud by Cahuzac.
Asked if the Swiss public prosecutor's office could confirm the arrest, a spokeswoman said the Swiss authorities had issued an order to open a criminal investigation against Condamin-Gerbier for dealing in commercial information.
"The person was arrested on Friday, July 5, 2013. They are currently in protective custody," the spokeswoman said in a statement.
Condamin-Gerbier, a former employee at Geneva-based Reyl & Cie, has said has a list of French politicians who have undeclared funds in secret Swiss bank accounts. Reyl & Cie has repeatedly denied the claims.
On Saturday, Reyl & Cie said it had filed a criminal complaint against Condamin-Gerbier on June 17 alleging theft, falsification of documents and violation of professional and commercial confidentiality.
It said it had handed over all its evidence to the Swiss public prosecutor.
Cahuzac quit his job as France's budget minister in March, after coming under investigation for tax fraud, and said he had a foreign bank account holding some 600,000 euros ($790,000).
Switzerland is under international pressure to change its tradition of strict banking secrecy, which other governments complain enables many of their wealthy citizens to avoid tax.