A cash machine at an Oxford university building has been dishing out old five pound notes which were removed from circulation 18 months ago.

The Barclays ATM in the Gibbs Building of Oxford Brookes University, in Gipsy Lane, Headington, dispensed the illegal tender on June 27.

The notes, which feature railway pioneer George Stephenson, were discontinued in November 2003 because they were easy to fake.

Brookes IT officer Gareth Brown only discovered the money he had taken out of the machine was not legal tender when he tried to use it at the student union shop.

He said: "It was the first time in five years I had been to a cash machine because I never knew my pin number.

"It gave me two fivers which is unusual, as it normally gives tenners. I went to the shop and they said they couldn't accept it as the notes were withdrawn 18 months ago. It's unbelievable.

"Where has this money been kept and why is it being put in the cash machine?"

Roz Smith, county councillor for Churchill ward, exchanged Mr Brown's money while she was at the London Road branch of Barclays in Headington and said: "There were a lot of people in the queue who had to break off from work to go to the bank and get the notes changed."

A Bank of England spokesman sad that notes which had been withdrawn could be exchanged for legal tender at any bank.

Danny Reardon, Barclays spokesman, said: "It would be unusual for our machine to issue old notes. We will launch an investigation. We apologise to customers who were affected."