SOFIA (Reuters) - The European Union's banking watchdog urged Bulgaria on Monday to give depositors access to guaranteed funds at troubled Corporate Commercial Bank (Corpbank) group (>> Korporativna targovska banka AD Sofia) from Oct. 21, saying current restrictions were in breach of EU rules.

The European Banking Authority (EBA) opened an investigation last month into Bulgaria's central bank and its Deposit Insurance Fund to assess whether they had broken EU rules, which say depositors should be compensated within 25 days after their accounts have become unavailable.

The European Commission has also opened an infringement process against the country.

The central bank seized control of Bulgaria's fourth-largest lender and shut its operations in June after a ran on deposits triggered the country's worst banking crisis since 1990s. Tens of thousands of depositors still cannot access their money.

"The EBA has formally requested that the Bulgarian National Bank ensures that depositors of Corporate Commercial Bank ... have access to deposits protected under the Deposit Guarantee Schemes Directive by 21 October 2014," it said in a statement.

The EBA said the central bank should either allow access to guaranteed deposits -- up to 100,000 euros (79,162 pounds) for each depositor -- or order the insurance fund to pay out compensation. The fund should start paying out the compensation if the central bank declined to act, it added.

Bulgaria's interim finance minister has said the government is preparing legal changes to bring the country into line with EU deposit rules, and said customers could get access to their money in November, once the country decides whether to rescue the bank or let it collapse.

An earlier effort to rescue Corpbank was bogged down by political bickering ahead of Oct. 5 elections.

The central bank has said a decision on the bank's future should be taken by Nov. 20, pending the results of an international audit at the bank and to give current and other investors time to come up with a potential restructuring plan.

The EBA expressed concerns about the length of time it was taking to establish the financial situation of the bank, and the impact this was having on resolving the uncertainty for depositors and other creditors in Bulgaria and beyond.

Corpbank holds over 6 billion levs (2.41 billion pounds) of deposits, of which 3.6 billion are guaranteed, and the bank has also failed to make a final payment on a $150 million bond, sold to international investors.

The central bank said on Monday it had received the audit, carried out by accountants Deloitte, EY and AFA. It is expected to announce the results in the coming days.

An initial audit showed serious malpractices at Corpbank, according to the central bank, as well as a lack of sufficient information on loans worth 3.5 billion levs.

If the central bank establishes the bank's equity is negative, it could revoke its licence and seek its bankruptcy.

The central bank also said it had not received a rescue plan so far from Austrian consultancy EPIC, which had shown initial interest on behalf of current shareholders.

It has said EPIC has not provided documents to show it represents shareholders other than main owner, Tsvetan Vassilev.

Vassilev, charged with embezzlement, controls 50.6 percent of the bank, while Oman's sovereign wealth fund has a 30 percent stake and Russia's VTB Bank has about 9 percent.

Vassilev has denied any wrongdoing and blamed the run on the bank on a plot by his competitors in collusion with some state officials and prosecutors.

In a separate statement on Monday, Vassilev accused the central bank of finding false pretences not to discuss the bank's rescue, thus playing into the hands of rivals that want to liquidate the bank.

The businessman, who has turned himself in to authorities in Serbia and is awaiting a court ruling there on an extradition request by Bulgaria, is also under investigation by authorities in Liechtenstein on suspicion of money laundering.

The crisis has raised concerns over banking supervision in Bulgaria, prompting political parties, trade and employer unions to demand the central bank governor's resignation.

(Editing by Mark Potter)

By Tsvetelia Tsolova