Limits

The idea is that users will be able to use the "wave and pay" card in shops with special new card readers, such as newsagents, pubs, and coffee bars, as well as car parks and vending machines.

The card owners will simply have to wave the card close to the reader and will not need to use either a signature or a 4-digit pin number.

Any transaction over £10, however, will still need a pin to verify it.

"In addition, users will on occasions be asked to enter a pin for purchasers below £10," said Barclaycard's Ian Barber.

"The system is chip and pin and uses the same technological protocols as a standard credit card."

Concerns

Contactless chip cards have inspired security concerns, particularly with their use in official documents such as passports.

Some researchers claim already to have cracked the encryption used to safeguard the information on the chips to be used in US passports.

Mr Barber, however, said that the system Barclays was using - to standards established by credit card group Visa - was distinct from the US systems, and was secure.

Testing period

The trial will start with Barclays staff using the new cards and card readers inside their banks and other bank buildings. Visa Europe is helping organise the trial.

It will then be extended to a few shops such as certain coffee bars.

The trial will combine two distinct elements; one for the combined credit/Oyster card and the other for the contactless technology.

Mr Barber stressed that the Oyster and credit or debit accounts would still remain separate.

"If you tap the yellow Oyster pad at a tube station, to buy a ticket, money will be deducted from the Oyster account," he said.

"But if you pay for a coffee and a newspaper in a shop that will come from your credit or debit account."

Exclusive deal

The bank is confident that the combined credit/Oyster card will be popular, particularly in London.

But it will be relying on the trials of the wave and pay option before deciding on a definite commercial launch which would have national appeal.

The bank has struck a deal to try out the new cards and contactless readers with TranSys, the company that runs the Oyster card system with Transport for London.

The deal gives it the exclusive right, for three years, to put Oyster cards on its Barclaycard credit cards and Barclays Connect debit cards.

Other banks and credit card issuers are expected to adopt the "wave and pay" technology in due course.