Barclays, Lloyds, Halifax, RBS and HSBC are among firms who have sent customers letters that look like they are from outside firms when they are not, the Daily Mail reports.

The letters appear to be designed to put pressure on customers by making them believe requests for debt repayments have been passed on to third parties.

Energy giant Scottish Power and Anglian Water, which supplies families in the East of England, are also using the letters.

A major row erupted last week when it was revealed that payday loan giant Wonga had made up the names of two firms to harass people who were behind on loan repayments.

The firm was ordered by the City watchdog, the Financial Conduct Authority (FCA), to pay £2.6m in compensation to the 45,000 people affected.

The City of London police are investigating whether Wonga has broken one of several laws, ranging from the Theft Act to the Administration of Justice Act, which covers the harassment of debtors.

It later emerged the Student Loan Company was using the same tactic to chase graduates for their student loans, and it can now be revealed that the threatening tactics go well beyond the ‘legal loan sharks’ such as Wonga, with a string of household names using the controversial ploy.

Barclays has been using the name Mercers Debt Collections, while Lloyds, which is part-owned by the taxpayer, has used Sechiari, Clarke and Mitchell Solicitors, which is actually its in-house legal department. Its subsidiary, Halifax Bank of Scotland, has used the name Blair, Oliver & Scott to chase debts.

MPs and consumer groups last night said it was ‘dishonest’ for banks and utility firms to be ‘distressing and intimidating’ their customers.

Consumer Action Group founder Marc Gander said: “These are dishonest tactics, however they are widely used, even by so-called reputable companies.

“This is not just about Wonga. All the companies that employ these tactics, whether it is the Student Loans Company, the banks or utility companies, should face equal scrutiny and equal sanctions.

“Action needs to be taken.”