French prosecutors said Tuesday they had opened a formal investigation into Budget Minister Jerome Cahuzac for suspected tax fraud, adding that he was probably the person recorded on an incriminating audio tape.
Cahuzac, who is in charge of battling tax evasion, has denied any wrongdoing following a report by the Mediapart investigative website that he had an undeclared Swiss bank account until 2010.
Mediapart said he then transferred the money in the account to Singapore. It said it had a "trace" of a conversation between the minister and one of his former aides in which he allegedly fretted about the UBS account and then said he had "dealt with the matter."
Prosecutors said police experts had concluded that Cahuzac "is the man speaking" on the tape. They said they had decided to open a formal investigation into money laundering and fraud.
Cahuzac has dismissed reports of offshore accounts as "crazy claims". In a statement in December he said: "I have never had an account in Switzerland or any other place abroad."
He also denied figuring in the recording reported by Mediapart.
Mediapart claimed that Cahuzac closed the account in 2010 just before becoming head of the finance committee of the National Assembly. It alleged he made a discreet trip to Geneva to close the account.
The minister, who is a civil plaintiff in a judicial probe into French residents suspected of tax fraud, has announced sweeping measures to fight tax evasion.