Faulty payment machines at Oxford's Westgate car park need to be replaced at a cost of £130,000.

Councillors at Wednesday's city council executive board meeting were warned that if a major failure occurred, the local authority could lose £500 an hour because barriers would have to remain open so motorists are not trapped.

Drivers using the Westgate car park take a ticket to enter through an automatic barrier. When they leave, they have to insert the ticket into a machine and pay the necessary fee to get it endorsed, so they can activate the exit barrier.

Last month, the council drafted in extra security staff after exit barriers were ripped out, allowing shoppers to leave without paying.

Coins keep jam in the machines which are 12 years old, and council staff want to replace the system with a more user-friendly pay-and-display version.

Graham Smith, business manager for the council's car parks, told councillors that spare parts were no longer available from the manufacturers to maintain the machines.

He added: "To date, no income has been lost due to machinery breakdown but it is only a matter of time before a serious machinery breakdown will occur.

"It is also considered that the frequency of this magnitude of breakdown will increase once the machinery reaches this meltdown status."

Fifteen pay-and-display machines would cost £132,000, councillors were told.

At present, the Westgate is the only city centre car park where shoppers don't have to forecast their length of stay, but the mechanical problems are likely to lead to a change.

As part of plans to double the size of the Westgate shopping centre, the multi-storey car park would be demolished and replaced with an underground car park.

Councillors agreed in principle to changing the payment system at the Westgate. New pay-and-display machines could be relocated at other sites if demolition goes ahead.