Drivers who stray into bus lanes are to face £100 instant fines.

Brighton and Hove City Council plans to introduce digital traffic cameras at three sites in the city centre.

A survey by The Argus in the bus lane approaching the Clock Tower from Dyke Road suggests that clamping down on rogue motorists could become a lucrative operation. Between 3pm and 4pm yesterday, 122 drivers broke the law there.

Gill Mitchell, the council's environment spokeswoman, said: "We're not setting up this scheme with the intention of making money.

"Ideally, we'd rather not make any money at all from it because that would mean no one is driving in the bus lanes.

"These cameras are not designed to catch people out - they're there to try and improve the city's public transport system."

The cameras will be able to take dozens of pictures a day, beaming the images back to control centre that will send out fines to motorists.

Brighton and Hove is one of 24 councils that intend to take advantage of new legislation intended to free up bus lanes.

Motoring organisations argue they could be used simply to raise revenue.

Kevin Delaney, of the RAC Foundation, said: "Councils need to look very carefully at their bus lanes to avoid an awful lot of complaints from disgruntled drivers.

"Whether bus lanes have been set up to deliberately catch people or whether that is a consequence of poor design is irrelevant.

"The point is that, until recently, bus lanes were not well enforced and with the expansion of cameras we are seeing the shortcomings.

"Bus lanes are to improve traffic flow, not raise revenue."

In London, 21 boroughs operate bus lane cameras. In the year to March 2003, 426,000 tickets were issued, raising £5.4 million.

Paul Watters, a spokesman for the AA Motoring Trust, said: "People get genuinely annoyed and upset when they receive £100 notices for nipping slightly into a bus lane so as not to hold up traffic behind them."