Aaron Williams, from Park Avenue North, Spinney Hill, was picked up by a black cab at the top of Bridge Street, Northampton on Saturday after celebrating a friend's 21st birthday.

Realising he did not have enough money to pay the fare, the 20-year-old asked the driver to take him to the Morrisons supermarket in Kettering Road and wait for him while he withdrew cash at an ATM.

As insurance against him making off, Mr Williams, who has recently applied to join the Army, told the driver he was leaving his belongings on the seat, including a Nokia 6700 mobile phone worth £200, his keys and a wallet containing his driving licence.

But when he tried to get back in the cab, the driver allegedly snatched his money and bank card and sped off.

Mr Williams' mum, Beverley, said: "Its absolutely disgusting. You tell your children always to get a taxi, don't catch a lift with any strangers and it looks like it may have been the taxi driver who was the danger all along.

"He's waiting for a call to be told whether he's been accepted for the Army. He wants to go and fight for his country and he won't even know if he can now."

Mr Williams said: "I left those things in good faith because I know taxi drivers get people doing a runner all the time. It's unbelievable someone would do it to me instead."

Joe Matthews, of Northampton's Hackney Carriage Association, said: "Sometimes you get drivers from outside the town coming here so it may not be one of ours. It's a very odd thing to happen to a passenger."

Insp Carl Sturman said: "We are investigating but have not yet spoken to the taxi driver on this alleged matter.

"However it's quite an unusual for a passenger to be the victim of a crime. It's more often the other way round," he added.