£70bn cost to the economy

London's economy faces a "hugely damaging" £70million bill when the Tube is brought to a halt by tomorrow's strike.

Business groups said the 24-hour shutdown will force hundreds of thousands of workers to stay at home.

It could also jeopardise London's Olympic bid, deter foreign investment and slow down efforts to modernise the Underground, they warned.

Irving Yass, policy director at the London First business organisation, said: "We will be lucky if 25 per cent of people working in central London make it in. About 400,000 come in by Tube and the buses do not have the capacity to take anything like that. Not many more people can get in by car, either, because of congestion and the lack of parking.

"Some people will cycle or stay with friends but even so, if 100,000 people manage to get in by various means they will be doing well. The economic loss from that is enormous and hugely damaging."

Colin Stanbridge, chief executive of the London Chamber of Commerce said: "There is no conceivable justification for this level of inconvenience." A spokesman for the Corporation of London said: "The financial cost is bad enough, but that is secondary to the disruption."