Beep Beep - the ad you get by Bluetooth as you're walking past

In what is believed to be the first case of its kind, members of the public passing branches of HSBC have received messages from the financial giant on their handsets by Bluetooth technology.

Hundreds have been sent the unsolicited commercials when close to two of the busiest London branches, Regent Street and Canary Wharf.

The technology was invented to send information between electronic devices without the need for wires but is typically used only to send pictures and files between friends and business people.

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Passers-by at the Regent Street branch on Friday were sent video files promoting HSBC's cash ISA.

The first screen flashed up "Look, no tax!', then changed to read "Open a Cash Mini-ISA now and we'll give you £2 to be shared equally between Earthwatch, The Climate Group and WWF'.

The final screen gave a number to text for a telephone call-back or suggested asking in the branch.

HSBC, which has 8.5million current-account holders, did not publicly announce the new system but has been secretly testing it for two months.

A hidden Bluetooth 'box' inside the bank branch searches the nearby area for Bluetooth-enabled mobile phones.

Those who have the facility activated on their handset are then sent a message asking if they will accept a free download from the bank.

If they accept, a full message is transmitted giving information about one of the bank's products or services.

The passer-by can refuse the information, in which case no message is received. The technology can also spot whether someone has already been contacted, to make sure they do not get repeated messages from the same campaign.

HSBC says feedback from customers and passers-by has been 'positive' but The Mail on Sunday found a more lukewarm reception among shoppers.

Stuart Green, 44, from Aylesbury, Buckinghamshire, was sent the message offering the download but refused it.

He said: "To be honest, I wouldn't accept it. I don't risk it with anything that I haven't actually asked for myself. There are too many scams around."

Sarah Thomas, 36, of Finchley, North London, said: "I get enough spam on email and in the post - the last thing I want is messages coming up while I'm walking down the street.

"What if all the shops started doing the same?'

Bluetooth is the name for a short-range radio-based technology, capable of sending speech and data across a distance of ten metres.

It is named after the Danish king Harald Bluetooth who united Denmark and Norway - echoing the initial aim of the technology to unify the telecom and computing industries.

The move recalls the personalised talking advertisements featured in futuristic film Minority Report, starring Tom Cruise, where billboards flashed to life as people walked by.

HSBC says the scheme is being piloted during branch opening hours but could be extended. "It is an exciting new way of communicating,' it said.