Nearly 100 London suburban trains had to be withdrawn from service after drivers refused to operate them because of safety fears.
South Eastern Trains had to cancel about half its services for South London and North Kent while safety checks were undertaken on its 97 four- coach Networker trains built at ABB York over the past three years.
The Health and Safety Executive ordered the checks after a coupling broke on one of the trains over the weekend. A spokesman for South East Trains admitted that faulty couplings had been found on several other trains but refused to say how many. He said: "We are checking all the trains for fatigue cracks in the couplings and this will take several days."
Commuters are likely to find their services disrupted over the next few days as nearly two-thirds of South Eastern's Networker fleet are checked. As the trains are given the all-clear, they are being put back into service. Networkers built at GEC Alsthom are not affected.
Last night Brian Wilson, Labour's transport spokesman, predicted that disruption would last for several weeks. He said: "There's a lack of couplings and repairs will take a long time. If this had happened after privatisation, the train company could have been bankrupted."
Following the initial incident, South Eastern ordered that the trains should run with the internal doors between carriages locked but the drivers refused to operate them because of concern that if the coupling broke, the two halves of the train might collide. There is an automatic brake but the drivers felt that there was still a risk of a collision if one part braked faster than the other.
The company had earlier accused the train drivers of taking "inappropriate action" but Lew Adams, leader of Aslef, the train drivers' union, said his members had been vindicated in their decision to refuse to operate the trains.
"We talked to the company throughout Monday, trying to persuade them that locking doors simply wasn't the answer to the problem. How would people escape if there was a fire? What would happen if passengers needed to be evacuated if there was an accident? They wouldn't listen to us and tried to run the trains, but the drivers were having none of it."
Mr Adams said his members did not need to conduct a ballot in order to refuse to work the trains because they were not taking industrial action. He pointed out that legislation provided for a refusal to drive trains where people were in serious and imminent danger.
"If we had had tried to ballot our members and given management seven days' notice, it might have been too late."
A spokeswoman for the Health and Safety Executive (HSE) said its officials first heard about the problem on Sunday. Asked why drivers had to take action before the trains were taken out of service, the HSE said it could not take at face value what was being reported. "We needed to look into it to see if there was any validity in ithe complaints before we took any precipitate action."
The HSE finally took the decision yesterday after seeing the results of ultrasonic tests, the spokeswoman said.