The points on the railway in Cumbria where a Virgin Trains train derailed on Friday of last week were faulty.
The crash caused the death of one person and injuries to a number of others.
A stretcher bar between the points on the West Coast main line at Grayrigg near Kendal was missing.
The bars join the moving rails, keeping them a set distance apart.
This is a chilling echo of what happened at the Potters Bar rail crash outside London in May 2002.
The Cumbrian track was inspected three weeks ago, said Network Rail’s chief executive John Armitt, but it should have been checked at least once since.
Checks are supposed to take place weekly and there is a full mechanical survey every 13 weeks.
Another train was just minutes from disaster as it narrowly avoided ploughing into the crash wreckage.
John Tilley of the RMT rail workers’ union said, “It was lucky that it stopped a couple of hundred yards up the track when the driver was alerted to the crash.
“But there were minutes in it. There could have been carnage.”
RMT general secretary Bob Crow warned that a Railways Accident Investigation Branch inquiry was likely to prove “insufficient” to prevent further tragedies.
He added, “It is our contention that the public inquiry, in addition to establishing the facts of the accident, should also examine the adequacy of Network Rail’s management systems because of the fragmentation of engineering work that still afflicts our railways.
“I am extremely concerned that there are still contractors, subcontractors, labour-only agencies and one-man-and-a-trolley outfits let loose on the tracks under Network Rail and this should form part of the remit for the public inquiry.”