Traffic wardens are allowed to block bus lanes when stopping to give a driver a parking ticket, Sunday Life can reveal.
The revelation came after two enforcement officers were pictured parked in a 12-hour bus lane while ticketing a motorist who had parked on the pavement.
When asked about the situation a spokesperson for the Department for Infrastructure, which is responsible for traffic wardens, said they were allowed to do so.
"Parking enforcement is a statutory function carried out on behalf of the department by traffic attendants," they said.
"Occasionally, when traffic attendants are carrying out their duties they may have to park in contravention of traffic restrictions and there is a concession in place which permits this."
Sunday Life had asked why two officers were parked in the 12-hour Glider and bus lane on Oxford Street in Belfast city centre.
They had stopped to put a ticket on a car which was parked on the adjacent pavement on October 29.
But rather than parking their three-wheeled scooters on the footpath beside the vehicle, they left them in the bus lane, facing the wrong direction.
The lane in question is used by the G1 Glider route which runs between east and west Belfast.
Should a motorist do the same and get caught they are liable for a £90 penalty, which is reduced to £45 if paid within two weeks. In the past four years, £4 million in bus lanes fines have been collected in Belfast, with a single camera on Donegall Square East responsible for £1.5m alone.
According to figures released earlier this year by the department, £5.34m was spent upgrading bus lanes for the introduction of the Glider system.
Parking enforcement in Northern Ireland is provided by the firm NSL Services Group, under contract from the Department of Infrastructure.
It is responsible for issuing Penalty Charge Notices (PCN) for illegally parked vehicles.
Certain parking issues, such as dangerous parking or causing an obstruction, remain the responsibility of the PSNI.
While parking on the footpath is not banned outright it is unlawful at an urban clearway, such as a bus lane.