BBC One claims the undercover reporter on its 'Whistleblower' programme at 9-10pm witnessed Barclays employees mis-selling products, lying to customers to generate sales, forcing customers to pay unlawful charges, offensively stereotyping customers and breaching security measures.
The programme follows a nine-month investigation by BBC reporter Amanda Egbujo, who went undercover as a call centre worker in Sunderland and as a cashier at a Barclays branch in Surrey.
Egbujo was encouraged to follow stereotypes to spot good customers. Her co-workers suggested customers from Liverpool are saddled with debt, Welsh men always want a new car and Scots do not want to talk.
The BBC decided to undertake the investigation after being contacted by a former Barclays employee who disapproved of the practices she encountered working at one of its call centres.
Barclays has issued a statement to defuse the negative publicity. A spokesman said: "We pride ourselves on being a responsible institution that puts its customers first.
"I don't think what you've seen is any way representative of the way in which Barclays does business, and I'm sure our millions of customers would tell you exactly the same thing."