The £1 million prediction made over Edinburgh's low emission zone

Scott Arthur said the initial figures for those penalised for driving into the city centre in non-compliant vehicles were due to be published next month and may need to be revised upwards because of the scale of fines levied in Glasgow’s LEZ, where enforcement started a year ago.

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He said the council may even receive sufficient income from the fines to cover the running costs of the scheme in its first year.

However, Neil Greig, the Scotland-based policy adviser to the IAM RoadSmart road safety charity, warned at the Roundtable of the dangers of councils coming to rely on income from such motoring fines.

Glasgow City Council has raised some £1 million in fines in the first ten months since enforcement of its LEZ started in June last year. Dundee started enforcement on May 30, and Edinburgh and Aberdeen on June 1.

Only vehicles meeting the latest pollution standards – such as petrol cars since 2006 and diesel cars since 2015 – are permitted in the LEZs. Drivers of non-compliant cars face £60 fines, which are halved if paid within two weeks but doubled for each repeat offence up to a maximum of £480.

Mr Greig told the Roundtable at The Scotsman Hotel, the newspaper’s former offices in Edinburgh: "If you get £1m of income, you are going to start to rely on that and there’s not much incentive to reduce it or improve signposting.

"It comes down to trust. You're asking drivers to trust a council that doesn't seem to be able to fit the potholes or keep the city centre particularly clean sometimes, to take all that money out of the economy and put it back in the right way and see some benefit from it, because at the moment we're not seeing any real benefit from extra spending on potholes. It's become a huge issue, particularly in Glasgow.

"I was surprised by the impact the LEZ had in Glasgow – the negative publicity and the money raised. But for businesses and individuals who have older vehicles and have to get into the city centre, it is a huge problem.

"Charities, night workers – a lot of people – are driving vehicles into the city centre. It's almost like a hidden economy that this was going on - people having to use these older cars and not able to change them very easily.”

Mr Greig called for roadside checks to crackdown on badly-maintained vehicles, which he said caused a disproportionate amount of pollution.

Mr Arthur said: "In Edinburgh, because of what's happening in Glasgow, fine levels might be higher than we expected. So it might be this year it pays for itself.

"But vehicles are being replaced all the time, and every day the fleet coming into Edinburgh is becoming cleaner, so fines are going to reduce.”

Jo Davidson, director of policy for Edinburgh Chamber of Commerce, told the Roundtable it remained concerned about compliance levels among vans and taxis as they had the lowest rates but were the most relied on by businesses.

She said: "The big issue for us is how enforcement will play out  – will it be punitive, or help to bring people on the journey of compliance?

"There's a very big difference between those who are unwilling to comply, in which case penalties are there, and those who have been unable to comply, particularly smaller businesses who are still facing very significant economic challenges.

"For some businesses, it's not that they've been unwilling to retrofit [vehicles], they just haven't had the financial capacity or there's been an issue with the availability of skilled people for retrofitting some vehicles.”

Ms Davidson said there was also a lack of awareness of the LEZ’s boundary, which was significant for delivery vehicles coming from other areas. However, she said businesses backed the scheme, which they had accepted as being inevitable.

Rachael Revesz, a volunteer for pedestrians’ campaigners Living Streets Edinburgh who is also a trustee of sustainable transport body Transform Scotland, told the Roundtable she was “massively” supportive of the LEZ but wanted it extended city-wide, which would also make the boundary clearer.

Calling for bolder action to reduce car traffic, she said: "It feels like we are tinkering round the edges literally and metaphorically.

"Some levels of pollution have been falling but the number of cars is always increasing and will increase as we build more houses.”

Ms Revesz said her “ideal shopping list” included enforcing engine idling and speed limits, 24/7 segregated bus lanes, ensuring buses on cameras could be used to enforce them, and making bus travel free for everyone.

She criticised the council’s plan to curb through traffic in the city centre. She said: "Too much attention is being paid to creating convenient diversionary routes for drivers rather than fulfilling the ultimate goal of deterring driving in the first place.”

Mr Arthur said the council’s target of cutting traffic by 30 per cent by 2030 – compared to 20 per cent across Scotland – would also improve air quality, but would require a major increase in bus travel.

He said: “To be serious about reaching that target, more walking and cycling would be great, but public transport has to take a lot of that lifting on board in moving people around.”

Mr Arthur admitted none of the political parties on the council had been happy with the zone area – bounded Queen Street, Abbeyhill, The Meadows and Palmerston Place, near Haymarket – but it had been the “least worst option”.

He said: “Some wanted it bigger, some smaller and some even wanted aeroplanes going over the city included.”