bbc news articleA minicab drought is afflicting passengers, with scores of social media complaints of cabs being unavailable or cancelled at the last minute.
Drivers in London say "rotten rates" after a switch in pay levels last Christmas mean as many as 80% of journeys are being turned down.
But Uber, the capital's biggest minicab operator, says any issues are being caused by a spike in demand.
It said it was trying to recruit 20,000 more drivers to address this.
However, Uber driver Mehmet, a member of the App Drivers & Couriers Union (ADCU), said the pay-rate change last year was a key reason people were finding it harder to get a cab.
The company's rides are now being set at a fixed price of £1.25 a mile, Mehmet said - well below the £2 break-even point for drivers.
It is lower than the £1.50 rate he was getting in 2017, he added - and well below the £4 black cabs charge - which he says is leading to a spike in journeys being turned down by drivers.
I'm part of a Facebook group of about 600 drivers," Mehmet said. "Rejection rates are about 75-80% at the moment.
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Uber is sending us £8 fares for journeys through central London that take an hour and 15 minutes with speed restrictions and diversions."In my 17 years as a driver these are the lowest fares I've had and it's really damaging our earnings."
Another Uber driver and ADCU member, Hadi, agreed, saying London has some of the lowest fares in the UK. He told the BBC fares had been cut four times since 2014, meaning drivers could no longer afford to take many passengers.
"We're talking about 80% (of fares) being rejected," he said.Uber 'willing to change' as drivers get minimum wage
Uber drivers are workers not self-employed
"Drivers are looking at some of these prices and thinking, 'it's not worth it, so I'm not going to take it'.
"Customers are complaining they cannot get home but the drivers don't set the rates. It's not the drivers that should be blamed, it's Uber, but when we ask them for £2 a mile it's falling on deaf ears."
Shweta Aggarwal, who lives in the Hertfordshire commuter town of Rickmansworth, normally gets an Uber into central London about once a fortnight.
She said she had noticed a shift away from drivers being keen to pick up a longer fare like hers.
"Ubers are cancelling on you more and more. They say they're coming but then you're left stranded. Our friends in central London also say it's almost impossible to get an Uber and there's literally no choice.
"When it comes to Uber they've definitely become more unreliable and there's a point at which it's not worth it and we'll just get a train instead."
Steve McNamara, who represents black-cab drivers through the Licensed Taxi Drivers' Association, said plenty of drivers and cabs were available but excessively low rates in the minicab industry were disrupting the trade.
"We're aware that some of the private-hire companies are having enormous trouble covering work and the reasons for that are crystal clear," he said. "Many are working incredibly long hours for little pay.
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Mr McNamara added that the drop in black-cab numbers - there are nearly 10,000 fewer black cabs in London than there were in 2011- was partly due to the switchover to electric vehicles and a move towards multiple drivers sharing a vehicle between shifts.