Shares in German payments company Wirecard have fallen more than 60% after the firm said its auditor had raised questions over cash balances worth €1.9bn (£1.7bn).

Auditors EY had refused to sign off on Wirecard's accounts, saying it was unable to confirm the money existed.

The missing sum amounts to about a quarter of its total balance sheet.

Wirecard said there was evidence of "spurious" figures intended "to deceive the auditor".

Wirecard joined Germany's blue-chip Dax 30 share index two years ago. At the time, it was valued at €24bn, but following the latest share price crash this has fallen to just €4bn.

The scandal came to light after a series of articles in the Financial Times last year focusing on alleged accounting irregularities in Wirecard's Asian operations.

The missing money was supposed to be held in accounts at two Asian banks and had been set aside for "risk management", Wirecard said.

However, EY auditors said the banks had been unable to provide the account numbers.

Wirecard said there were "indications that spurious balance confirmations had been provided" by a trustee "in order to deceive the auditor and create a wrong perception of the existence of such cash balances or the holding of the accounts".

"The Wirecard management board is working intensively together with the auditor towards a clarification of the situation," said the company.