Frozen accounts: More than 3 million people have opened an account with Monzo since it was granted a banking licence in 2017

Digital bank Monzo has been accused of freezing accounts without explanation, leaving some customers struggling to pay bills and buy food.

The startup has even directed those affected to food banks or charities if they have complained of having no cash, according to BBC One consumer programme Watchdog.

Banks have a legal obligation to freeze accounts that show signs of suspicious activity and report them to the National Crime Agency (NCA).

While the NCA is investigating, they are not allowed to tell the customer what is going on because this is an offence called 'tipping-off'.

But this process should take only a week, and experts have accused Monzo of being heavy-handed.

More than 3 million people have opened an account with Monzo since it was granted a banking licence in 2017.

One mother told the BBC that she had been left unable to pay her rent, bills or buy food after the bank had shut down her account.

She said it gave her details of food banks when she asked for help. 'You contact [Monzo] on the online chat and they'll just say exactly the same thing, as if they are reading from a script,' she added.

One mother told the BBC Monzo had directed her to food bank after she was left unable to pay her rent, bills or buy food after the bank had shut down her account (file picture)

She said she had not been able to speak to anyone at the bank, explaining: 'They've blocked my mobile number.'

Another customer said Monzo told them to seek help from a homeless shelter.

Financial crime solicitor Arun Chauhan said Monzo was 'going too far' and that 'the wrong people's accounts are being frozen'.

He added: 'It seems their compliance procedures haven't kept up with their growth.'

Monzo chief executive Tom Blomfield said that Monzo was no 'more or less exposed than any other bank'.

He said, on average, it takes the bank 2.7 weeks to return money to a customer once their account has been given the all- clear and that it is 'working hard to make this shorter'.

The bank said: 'No conclusions can be drawn based on a bank refunding those whose accounts have been closed.

'It does not mean that they have been treated unfairly.

'Without context, which we are prohibited from sharing by law, it is incorrect to reach a conclusion about why accounts have been frozen or closed.'

m.dilworth@dailymail.co.uk