Manchester council is being forced to cancel nearly 20,000 fines issued to drivers using bus lanes in the city.
A legal loophole means that because the cameras were not certified correctly, the fines issued between October 2006 and December 2008 are invalid.
More than £544,000 was collected in fines, and those issued with a ticket will now be able to reclaim their money.
Vicky Rosin, the council's director of neighbourhood services said: 'We apologise for this mix-up. Anyone who thinks they have been issued with a Penalty Charge Notice by one of these cameras during the period in the past when they were not approved can contact the City Council. We will look at each ticket on a case by case basis.'