By Martin de Sa'Pinto
ZURICH (Reuters) - A Swiss court said on Thursday it has rejected an appeal against the continued detention of a witness in a French tax evasion investigation, who is being held in jail over allegations that he breached Swiss laws on banking secrecy.
Pierre Condamin-Gerbier, a former employee at Geneva-based private bank Reyl & Cie, has said he has a list of French politicians with undeclared funds in secret Swiss bank accounts and in July appeared before a French parliamentary commission investigating tax fraud.
He was arrested shortly after his return from France when an investigation was opened against him into allegations of dealing in commercial information.
Reyl & Cie said in a statement late on Wednesday that it has no French residents holding political office in France among its clients.
In April former French government minister Jerome Cahuzac had admitted to holding a secret 600,000-euro ($800,000) Swiss bank account after months of denying it. He had resigned as budget minister two weeks earlier while still protesting his innocence.
Reyl & Cie has filed a criminal complaint against Condamin-Gerbier alleging theft, falsification of documents and violation of professional and commercial confidentiality.
In rejecting Condamin-Gerbier's appeal against being held, the federal criminal court in Bellinzona said in a statement that custodial measures were appropriate given the weight of evidence against him and the risk that he could try to leave the country. The Swiss federal prosecutor's office said Condamin-Gerbier was being held in prison but declined to say where.
Switzerland has come under growing international pressure to change its banking secrecy laws, which other governments say enables many of their wealthy citizens to avoid taxes.
Herve Falciani, a former employee of HSBC's private banking unit in Switzerland who gave evidence at the same French parliamentary commission investigation is wanted in Switzerland on charges of stealing data on tens of thousands of bank accounts that a number of European countries have used to pursue suspected tax evaders.
Falciani fled to France in 2009 after HSBC discovered the data leak and put him under investigation.
In May Spain ruled against extraditing him to Switzerland because the charges he faces there are not considered crimes under Spanish law.
(Editing by Greg Mahlich)