Furious London taxi drivers may again bring gridlock to the city's streets after Westminster Council refused to backtrack on a controversial minicab marshal scheme across the West End.

Black cabbies say the scheme allows mincabs to 'rank' in the heart of London, a privilege reserved for taxis under the Public Carriage Office's licensing rules.

The pilot scheme is due to run until then end of the month, but the council is deciding whether to introduce marshals to other central London streets.

Hundreds of cabbies took part in a 'drive-in' protest, on Thursday, February 5, against the marshalling scheme, which comes as the trade faces its leanest times in memory. Taxi groups say fares are down 30 per cent since December.

Westminster Council, which set up the scheme with the Heart of London Business Alliance, says it introduced the marshals to provide safe transport to and from the West End, making it harder for touts and illegal minicabs to operate.

Despite a 44 per cent fall in cabrelated sexual offences since 2002, police still fear rogue minicabs are preying on drunken revellers - more than 100 attacks were reported in 2007.

Minicabs can now gather at a bus bay in Whitcomb Street, Leicester Square, from Thursdays to Saturdays, between 9pm and 4am.

Uniformed marshals take customers to a booking booth - run by West 1 Minicabs - and guide them to the first available minicab.

The London Taxi Drivers Association says the scheme oversteps the rules on running minicabs, by allowing them to wait for hire on the street - in breach of the licence agreement that states minicabs must be pre-booked.

"By approving this rank of minicabs where they can wait around the corner for customers, the Public Carriage Office are letting them behave like taxis," says Bob Oddy of the LDTA.

"There's a principle at stake here and if we let it go, the whole system will fall down. It will also have a major impact on our trade, which is already 30 per cent down this year due to the credit crunch. Taxis should be taxis and minicabs, minicabs."

Refuting accusations the marshal scheme is in effect a minicab rank, Martin Low, director of transportation at Westminster City Council, said: "This is about getting people home safely at night.

"Unfortunately, there are problems with unlicensed minicabs in central London.

"This marshalled service was introduced so people can book and pay for a minicab and then be escorted to their safe, registered cab home.

"It was never intended to replace black cabs, who offer an excellent service."

But taxi drivers are unconvinced, claiming the industry is under unparalleled pressure as customers tighten their belts.

Mr Oddy also urged the Public Carriage Office to stop issuing new cab licences during the recession - a call the PCO has so far ignored.

"Demand for taxis is down, so it makes no sense at all to have more taxis hitting the streets, at least until people have more money in their pockets."