Politicians from all sides have demanded urgent safety action following a second London Underground derailment within 48 hours.
Politicians don't want Londoners to panic about Tube travel
The London Assembly is to hold an emergency session in the wake of the incidents on Friday on the Piccadilly Line and the one which left seven people injured on Sunday morning in Camden in north London.
Lynne Featherstone, chairman of the London Assembly transport committee, said: "It beggars belief that there have been two derailments in less than 48 hours.
"There appears to have been a catastrophic failure of the Tube's maintenance and London needs answers now."
Questions have been raised whether there might be any link between the accidents and the fact maintenance had been switched to private companies under the government's public private partnership (PPP) of London Underground earlier this year.
Bob Crow, general secretary of the Rail Maritime and Transport Union (RMT) - the UK's largest rail union - said he would recommend a strike ballot unless maintenance contracts given to the private companies earlier this year were immediately suspended.
Ms Featherstone said: "The committee will be holding an emergency session this week to ask the Mayor what is going wrong and what he is doing to prevent these dreadful accidents from happening again."
London Mayor Ken Livingstone said the derailments had raised "grave questions about the safety of the system".
He said a full inquiry into the causes of the incidents would be conducted by London Underground.
Bob Kiley, Transport Commissioner for London, who was a fierce opponent of the PPP system set up to finance the Tube, told BBC One's The Politics Show: "I'm not a big believer in coincidence... so that, when you get two incidents like this within three days of each other, it's a cause of great concern.
"First of all we have to get to the bottom of these two incidents and, second, we have to now take steps to ensure that these things can't happen again.
"The average person is going to think, 'can I really use the Tube if two of these things happen within three days?'
"That's a legitimate question to be asked and that's one that we and the PPP (public private partnership) companies are going to have to answer."
Roger Evans, London Assembly Conservatives' transport spokesman, said: "We are getting to the state where Londoners are losing confidence in the safety of their main form of public transport. London Underground need to urgently let commuters know the state of their infrastructure and not hide it from the public."
Shadow transport secretary Tim Collins urged politicians not to overreact to the incident.
"It is imperative for everyone, including opposition parties, not to
create an atmosphere of over-reaction and panic.
"The Tube remains the safest
means of travelling around the capital city and no-one should give any other impression," he said.
The Liberal Democrats' London spokesman - and mayoral candidate - Simon Hughes, told BBC News 24: "There is serious cause for concern, not for panic but for concern, and the obvious things that can be done immediately to reassure the public must be to instate a daily track check and a daily tube train check."
"It must be in everyone's interest to spend the money to do the checking, to put in the resources and to review the effectiveness of the checks that are done... currently not good enough it would appear."
Asked if the PPP arrangement for running the underground was to blame, he said: "It would be easy to argue that, but that's not a very productive argument at the moment, in the sense that there is a contract in place.
"I like others opposed the private-public partnership, but that's been decided for the time being and at the moment we have to make sure for the passengers that those who do the job do it properly."
Hughes: Money must be spent right
Asked about Bob Crow's call for the suspension of the firm in charge of maintenance Mr Hughes said: "Legally it would be difficult to do that, I don't think it would be easy legally to justifiably suspend the contract. The public require something else other than great arguments between lawyers.
"I think they want better checks, better reliability, more frequent inspections and better inspections, and that can be done now. You don't have to argue about who's doing it.
"The key issue for the private sector is that it has got to have money spent on safety, not money spent putting the profits up."