The banking industry has warned that millions of business and personal account customers are leaving themselves open to fraudsters who pose as official bank executives.

The warning came after the British Bankers Association (BBA) conducted research into customers’ responses to common scams over the phone, via email or through text messages.

Based on its findings, the BBA says 8 million are vulnerable to ‘voice phishing’, in which fraudster use sophisticated tactics to get customers to give up private details over the phone.

It said 4 million might transfer money into a “safe” account if asked to do so, while 3 million would be willing to carry out “test transactions” online. A further 1.7 million would hand over their card to a courier if presented with ID.

In response the BBA has published a leaflet outlining eight things that legitimate banks will never ask customers to do:

1) Ask for your full PIN number or any online banking passwords over the phone or via email

2) Send someone to your home to collect cash, bank cards or anything else

3) Ask you to email or text personal or banking information

4) Send an email with a link to a page which asks you to enter your online banking log-in details

5) Ask you to authorise the transfer of funds to a new account or hand over cash

6) Call to advise you to buy diamonds, land or other commodities

7) Ask you to carry out a test transaction online

8) Provide banking services through any mobile apps other than the bank’s official apps

Anthony Browne, chief executive of the BBA, said: “Being defrauded is a devastating experience for anyone which is why we are launching this campaign. The more people know about fraud, the less likely they are to become victims.”