The cash fare for a single zone 1 Tube trip will soar from £3 to £4 next year, while the cash fare for a single bus will rise to £2 - a 33 per cent increase.

In a move designed to let people switch from cash to the Oyster smartcard, Oyster fares for single journeys have been frozen.

Card fares will remain £1 on all buses, and - depending on the zones - between £1.50 and £5.50 on the Tube.

It means that on many journeys, cash fares will be double those charged on Oyster. On the Undergroud, the difference between single cash and Oyster journeys could be as much as £2.50.

"I want to see every Londoner paying the lowest possible fares by switching to Oyster," London mayor Ken Livingstone said.

Brian Cooke, chairman of travel watchdog London TravelWatch, said he was "extremely disappointed" at the cash fair increase.

"There are still not adequate facilities for visitors and tourists to buy Oyster cards easily, so this will really hit hard. London is already an expensive city - it has now become even more expensive for visitors to the city," he said.

"If cash fares will continue rising, it is imperative that buying Oyster cards from elsewhere in the country and internationally is made much easier. Otherwise, people will just be priced off the tube and buses altogether and might think twice about coming to London."

Over the last year, cash use has halved on public transport to 6% of Tube journeys and 5% on buses.

Clamp-down on cheats

In a clamp-down on Oyster cheats, pay-as-you-go customers who do not touch in and out at the start and end of their journeys will be charged £4 charge from November onwards.

Other fare increases, to kick in next January, include:

  • Bus cash fares rise by 33% from £1.50 to £2.
  • The Oyster off-peak fare on buses will rise from 80p to £1.
  • The Oyster one day cap remains £3, which means card users will never pay more than £3 no matter how many trips they take on a day. Its cash equivalent, the One Day Bus Pass, is frozen at £3.50.
  • On the Tube, the daily Oyster cap remains 50p below the One Day Travelcard price.
  • Travelcards will rise by inflation plus 2%.
  • The Weekly Bus Pass increases in line with inflation from £13.50 to £14.

From next Easter, 11-year-olds will travel for free on the Tube and DLR, while under-16s with Oyster will pay only 50p on the Underground.

But in a new scrutiny report on transport fares, the London Assembly warns: "For Londoners on low incomes higher cash fares could mean public transport becomes unaffordable."

Low income groups make out 25% of London's population of 8 million, but only 12% of Oyster pay-as-you journeys, the transport consultant Colin Buchanan told the assembly.

It was unclear why Oyster take-up is slower among the poor, but the assembly called for more research.

The report also pointed out that there is no public consultation on fare increases in London, unlike Paris and New York. "Londoners should be able to have a say on such developments," the assembly said.

Increase 'less than promised'

Despite the hike in cash fares, the mayor said the increase in bus fares overall is two thirds less than he promised initially.

In 2004, Mr Livingstone announced that bus fares would rise by 10% above inflation for three subsequent years. However, due to "efficiency savings" the third increase will be restricted to 3.8% above inflation, he said.

Still, the increases caused an outcry among the Conservatives, who accused the mayor of "over-paying" bus companies while Londoners foot the bill.

In June Stagecoach sold its two London bus services to the Australian investment bank Macquarie for £263 million. Of that, £120 million was profit - an 83% return on the bus firm's investment.

"With the average load of a bus just 15 passengers, you have to ask why we are paying bus companies to run empty buses," said Roger Evans, transport spokesman of the London Assembly Conservatives.

"At a time when the cash fare has risen from £1.50 to £2.00, it is not fair on Londoners that the mayor is lining the pockets of investment banks."