Parking wardens have been unable to ticket motorists flouting limited time stop areas in Birmingham because their handheld computers are not working properly.
It means high streets and shopping parades where cars can park for one, two or three hours with no return for a certain period have not been fully policed since April 1.
Residents in one Sutton Coldfield town centre street have claimed motorists have realised this now flout the rules daily.
The handheld devices have not been programmed with locations of limited time parking areas, meaning the wardens cannot issue tickets.
Details were revealed by councillor Ewan Mackey, who had been contacted by a resident of Railway Road in his Sutton Trinity ward.
They had complained about cars outstaying their welcome, only to be told by a warden their computers could not issue a ticket.
Coun Mackey said the problem was an issue for businesses and residents which found their streets clogged with cars and it could also hit city council coffers.
He said: "Birmingham City Council have been and may still be missing out on a many thousands of pounds, which is vital at a time when money is tight.
"This is especially so as there is no indication as to when the problem will be rectified. I've not seen anyone ticketed in the last few months on the lower end of Railway Road, where overstaying is commonplace."
He was told the snag was due to an upgrade in the handheld computer software, in which a system called 3Sixty has been replaced with another called Rialto.
Officials have yet to input all the details of limited parking locations into the devices, meaning that tickets cannot be issued.
Labour cabinet member for transport Tahir Ali said the new system would eventually have "enhanced features" for limited time areas.
"In order to use this particular function to its fullest capacity, it is necessary to collate additional information for the limited wait locations. This is an ongoing task and locations will be updated on a continuous basis," he added.
Officials confirmed the devices still worked for other parking enforcement and that limited time bays could be enforced using a cumbersome 'work around'.
The Birmingham Post has launched a free app for iPad and iPhone. Download it here.