Auckland City may have 10 times more bus lanes than its Manukau neighbour, but it is imposing thousands of times more fines on drivers caught using them illegally.

Only six $150 infringement notices were issued for the 2009-10 financial year in Manukau, which has 3km of bus lanes.

In Auckland, 41,169 tickets were issued for for breaches on the city's 31km network.

In between was North Shore City, which issued 2639 notices for breaches on its 9km of "transit" lanes, usable by vehicles with more than two or three occupants as well as by buses.

Waitakere City, with only short bus "advance" lanes at some big intersections, issued no tickets.

Faced with a public backlash against its nearly $6.2 million of fines, Auckland City Council leaders say it is obliged to enforce Government regulations allowing car drivers to travel no more than 50m in a bus lane before making left turns.

But Transport Minister Steven Joyce said on Tuesday he expected some leniency from the council, and a Ministry of Transport spokesman confirmed late yesterday that local road control authorities had "discretion" in the way the rules were enforced.

"There are no mandatory requirements as to how enforcement is specifically applied," he said.

"Authorities need to ensure they apply a practical, sensible approach to enforcement."

Manukau parking operations manager Liz Hogan attributed the low number of tickets in her city to high compliance rather than staff leniency.

But it put cones on kerbsides 60m from main intersections, and nobody was fined for using a bus lane inside zones marked that way.

Auckland City bowed to pressure on Tuesday by announcing a trial of markers to show 50m points near main intersections.

Ms Hogan said a bus lane in Bader Drive, Mangere, was controversial when it was created in 2007 - in a year her council issued 4158 infringement notices.

That prompted an intensive publicity campaign in which large red signs warning of $150 fines helped reduce breaches to 16 for 2008-2009.

Manukau Mayor Len Brown said popular support for bus lanes would be essential for boosting public transport in the new Super City, which he is vying to lead, "but we will not be using tickets as revenue support".

His main rival in the Super City contest, Auckland City Mayor John Banks, has rejected accusations of revenue gathering. But he has acknowledged that an independent parking advisory board was charged with generating income to offset rates.

Mr Brown said he had learned from his council's "overzealous" policy in 2007, to put more emphasis on educating people about "what the bus lanes are for and why they are important".

Mr Banks did not want to discuss the disparity between the fines figures yesterday, but a spokesman said comparisons were difficult as traffic converged on central Auckland from throughout the region.