Taxis could be forced off the road by an age restriction on vehicles in Preston.
A ban on all cars more than 10 years old is being considered by licensing bosses at the city council in a bid to improve air quality.
But drivers plan to fight the plans which they say will inflict "financial hardship" on cabbies already hit by rising fuel, insurance and other costs.
The new rules, due to go out to public consultation on Friday, would be phased in between 2009 and 2014.
Vehicles over 15-years-old would be banned from April next year, and the age limit would be reduced by one year every year until 2014.
Mark Selley, secretary of the Preston Hackney Carriage Association, said: "We will fight tooth and nail against such a policy. We feel very strongly that it would force great financial hardship on drivers to make the council's job easier.
"It could render a £10,000 vehicle worth next to nothing. To impose a draconian policy ... it will force a lot of drivers out of business. This is a very emotive issue because drivers' livelihoods are at stake here.
"If they've got issues with quality of vehicles, it's due to the council's enforcement. What the council has to do is make sure owners and drivers are running their vehicles responsibly.
"You will see Hackneys that are 15 years old but are still perfectly reliable because they're purpose-built for the job."
The 10-year ban would affect 39% of Hackney carriages and 22% of private hire vehicles, around 120 vehicles. Only eight vehicles would be 15 years old or more on April 1, 2009.
Ribbleton Taxis boss Mick Rooney, who paid £4,800 for an eight-year-old Mercedes saloon 10 months ago, said cars were already required to have two MOT tests every year.
He said: "You're going to see a mass exodus from this job, then we'll end up with a shortage of taxis. Owner-drivers will disappear because they can no longer afford it so it plays into the hands of the big companies.
"It's not like you can stick the fares up because the trade's dying. You're better off really packing shelves in Morrisions."
Mike Thorpe, head of licensing at Preston Council, said: "We want to improve air quality and taxis are particular culprits of high emissions levels."
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