Financial firms are f­ailing to explain properly the protections people are entitled to when they pay by credit card, a consumer group has found.

Which? said many staff showed a poor knowledge of section 75 of the Consumer Credit Act.

Section 75 can make providers jointly liable for breaches of contract with a trader. Consumers are potentially protected for the total value, even if they only used their card for part of the payment.

Which? called current account and card providers six times each with the same scenario. Researchers said they were asking for advice on behalf of a relative who bought a £600 sofa, putting a £60 deposit on their credit card and paying the rest by cheque. The fictitious supplier went out of business before it was delivered.

Santander only got half of one reply correct out of the six times that researchers made the enquiry, while Tesco Bank came out top.

Which? awarded half points in cases where advisers gave a vague answer but indicated a refund might be possible, or said they could not give information without speaking to the cardholder.

No points were awarded for calls where the adviser said it would not be possible to make a claim, or that the cardholder would only be able to get the deposit that they had put on their card back.

Only one-third of advisers overall correctly explained that, if just part of an item has been paid for by credit card, it is still possible to claim for the full amount.

A Santander spokesman pointed to industry-wide confusion on the issue.

He added: "We wish to emphasise that, where section 75 claims are correctly identified, the majority are resolved to customers' satisfaction."