French Budget Minister Jerome Cahuzac is under investigation for tax fraud after a media report that he had an undeclared UBS account in Geneva which he then moved to Asia, prosecutors said Tuesday.
Cahuzac, who is in charge of battling tax evasion, welcomed the investigation, which he said would prove his "complete innocence," calling the allegations "absurd".
President Francois Hollande, other ministers and the Socialist Party have all given their support to Cahuzac.
The minister has denied the report by the respected Mediapart investigative website that he had an undeclared Swiss account until 2010, when he transferred the funds to Singapore.
Mediapart 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".
Investigators will "without further delay verify the authenticity and the contents of the recording... to reach the truth," prosecutors said in a statement.
Cahuzac has denied figuring in the recording reported by Mediapart, saying: "In the three-minute-40-second recording, there are four to five seconds when it could be me, but it seems it is not me."
Mediapart alleged Cahuzac made a discreet trip to Geneva to close the account.
The news site released an audio recording reportedly of Cahuzac admitting to having the account. In the recording, a man is heard saying: "It bothers me to have an account there, UBS is not necessarily the most hidden of banks."
Mediapart said it confirmed the information with a former tax official, who had raised the existence of the account in a memo to his superiors in 2008, and with a source at UBS.
In a statement after the report was released, Cahuzac said the evidence presented by Mediapart was neither "impressive" nor "convincing".
"I do not have, and have never had, a bank account in Switzerland or elsewhere abroad," he said. "No credible witness can assert or try to corroborate something that does not exist and has not existed."Mediapart is known for its investigative reporting and in 2010 broke the story of a campaign financing scandal involving ex-president Nicolas Sarkozy and L'Oreal heiress Liliane Bettencourt.
Cahuzac, who is a civil plaintiff in a judicial probe into French residents suspected of tax fraud, has announced sweeping measures to fight tax evasion.
He said he had asked his lawyers in December to get a certificate from UBS to state he never had an account nor any commercial transactions with the bank.
Little-known before being named a minister, Cahuzac began his career as a cardiologist before switching to the more lucrative world of plastic surgery, in particular hair transplants.
Elected to the National Assembly in 1997, he headed its commission on public finances and was named budget minister when Hollande formed his first government.
French media reported in October that Cahuzac's 300-square-metre (3,230-square-foot) apartment in Paris's exclusive 16th district was robbed, with thieves taking 100,000 euros ($130,000) worth of luxury watches.3