BANK staff have a "shockingly poor" knowledge of cash ISAs that could be leaving customers out of pocket, according to a watchdog.

Some 85 per cent of bank and building society staff contacted by Which? failed correctly to identify the new 2015/16 ISA limit of £15,240, and some banks had not updated their systems for their employees to look the figure up.

Which? made 156 anonymous calls to 13 of the biggest banks and building societies in January, asking for information about how to correctly transfer an ISA from one provider to another, how much could be transferred, rules around transferring between cash and stocks and shares ISAs, the next tax year's allowance and new Government rules on inheriting ISAs.

Posing as new customers to ask "straightforward" questions about savings limits and transfers, Which? said it found widespread confusion and poor information about long-established ISA transfer rules.

Bank staff referred Which? callers to the internet to find the answer to their question, or admitted they were not aware of stocks and shares ISAs.

Just 19 per cent of call handlers were able to correctly answer questions about new ISA inheritance rules.

The consumer group found the Co-operative Bank and Yorkshire Bank were the worst at providing accurate information, answering just 31 per cent of questions correctly.

But even the best performer, TSB, only managed to get 64 per cent of the questions right.

Which? executive editor Richard Lloyd said: "It is inexcusable for so many bank staff to have such a worrying lack of knowledge about the basics of ISAs, especially when it could be costing customers dear.

"Banks should have systems in place to ensure customers can rely on them to give up-to-date and accurate information.

"With new reforms announced by the Chancellor this week, the banks must do better, starting by properly equipping their staff so customers can be confident they're getting the right advice about how to make the most of their hard-earned savings."