PARIS (AFP) - France's Parliament on Tuesday kicked off a high-profile public probe into a major tax fraud scandal that has shaken the Socialist government and the squeaky-clean image it is seeking to project.

The special parliamentary commission will examine whether the government mishandled the scandal, in which former budget minister Jerome Cahuzac repeatedly lied about owning an undeclared foreign bank account.

Political heavyweights such as Finance Minister Pierre Moscovici, Interior Minister Manuel Valls and Justice Minister Christiane Taubira will be subject to a grilling, as will Mr Cahuzac himself.

On Tuesday, journalists at investigative news website Mediapart - which broke the story last December - kicked off proceedings by alleging police interference in the case.

Mr Fabrice Arfi, the reporter behind the revelations, said Mr Cahuzac's chief-of-staff Marie-Helene Valente had somehow become aware of a phone conversation between his boss Edwy Plenel and a source for the story.

He said Ms Valente had written an e-mail message to a third party on Dec 11, in which she mentioned the phone chat.

"The police were used to listen in on telephone conversations between Edwy Plenel and one of the protagonists in the case," Mr Arfi told members of parliament, without saying who the e-mail message was sent to or how he obtained it.

"We don't know if the interior minister himself is aware of these investigations," he said.

Mr Plenel, who was also questioned at the commission, denounced "the use of police to harm source confidentiality".

Mediapart revealed on Dec 4 that Mr Cahuzac had funds in an undeclared Swiss bank account. But the minister, who fought against tax evasion during his tenure in charge of the budget, consistently denied the allegations.

He finally admitted to having the account containing some 600,000 euros (S$970,000) in April after an official probe into the case was opened.

By then, he had already given up his ministerial position, and he subsequently resigned from Parliament as well. He was also kicked out of the Socialist Party.

The scandal shook France's Socialist government and damaged the squeaky-clean image that President Francois Hollande had sought to project, less than a year after he was voted into office.