A man whose phone was stolen last summer said the bank refused to help him when thieves accessed his apps and took £22,500 from his accounts.
Jacopo de Simone's mobile phone was taken from his pocket, and was locked and password protected. But within hours his bank accounts had been drained. He said: "I found both my current account and savings accounts had been drained of £22,500. I was completely shocked. I didn't know how this was possible.
"I don't access my phone using a pin code - I use facial recognition. My Barclays pin is different to my phone pin and they'd need to have both of them."
Barclays investigated, and said Mr de Simone was liable for all the losses, reports the BBC. He said: "They could not identify a point of compromise from the back end - to them it looked like the pin had been entered.
"The only thing they could suggest was that someone knew the code therefore it's gross negligence on my part apparently. I was totally in shock, incredibly unsettled. Eight months on Jacopo is still fighting his bank.
An investigator at the Financial Ombudsman Service (FOS) upheld Mr de Simone's complaint against Barclays which now has the opportunity to ask the ombudsman to examine the case.
Barclays said: "It wouldn't be appropriate to issue a statement until the matter has been fully assessed and FOS have been able to review the full circumstances of this case that we will be presenting to them."
Arun Chauhan, a trustee of the Fraud Advisory Panel charity, said: "The Payment Services Regulations say unless the consumer is significantly careless, they use the words grossly negligent, the bank should refund.
"It shouldn't be for the customer to persuade the bank that they've nothing to do with this."
