PARIS (Reuters) - French prosecutors have called on judges to confirm a one-billion-euro (721-million-pound) bail on HSBC Holdings (>> HSBC Holdings plc) to cover a potential fine over allegations that the bank helped customers dodge tax, a judicial source said on Tuesday.

The call came after HSBC appealed the bail, which it has called excessive. Magistrates are now due to decide whether to confirm it on June 15, with payment due by June 20.

HSBC declined to comment.

The amount of the deposit is almost half of the scale of the alleged fraud by HSBC's Swiss unit, one source familiar with the matter told Reuters previously.

The source said HSBC contests that figure, and the bank has always disputed the number of clients the French authorities have claimed its Swiss bank had.

HSBC would be the second big bank to have a hefty bail imposed on it by French magistrates in the last year, after Switzerland's UBS (>> UBS Group AG) had to provide 1.1 billion euro to the court to cover a potential fine for alleged money laundering. UBS's appeal against that bond was dismissed.

Under French court process, companies can be ordered to post a deposit when they are put under formal investigation, even if charges are not brought.

(Reporting by Chine Labbé, writing by Astrid Wendlandt, editing by Mark John)

Stocks treated in this article : HSBC Holdings plc, UBS Group AG