The father of one of two girls killed at an Essex railway level crossing has demanded a fresh inquiry into their deaths after new evidence was found.
Olivia Bazlinton, 14, and Charlotte Thompson, 13, died when a train hit them at Elsenham in December 2005.
A Network Rail risk report from 2002 had recommended new gates that locked automatically as trains approached.
Investigators said the report was "unlikely" to have changed their conclusions.
Olivia's father Chris Bazlinton, 62, said the document was not released for the inquest by Network Rail and that amounted to "a cover-up".
The Office of Rail Regulation (ORR) said the risk assessment report had also not been made available to it after the incident.
Officials there have now asked inspectors to review the document to see if it affects the outcome of a previous investigation it had carried out into the girls' deaths.
Olivia and Charlotte were killed by an express train at Elsenham railway station on their way to Cambridge for a shopping trip.
Mr Bazlinton said he believed the existence of the report would have affected the result of the inquest into their deaths and the subsequent civil court case.
He said: "I believe this goes very close to the top. I believe it's a cover-up, absolutely.
"We're calling for the true facts to come out. I want to know who decided not to send the document. We just need an inquiry."
The report, which was seen by the families for the first time three weeks ago, said: "Consideration should be given to incorporating Wicket Gates into Elsenham crossing controls and effectively locking them closed when trains are approaching."
The report was not part of the evidence listed in the 2007 inquest into the girls' deaths.
The inquest jury returned a verdict of accidental death.
A civil case against Network Rail collapsed last December after the operator did not mount a defence, and a compensation settlement was made out of court.
The ORR confirmed it had also just received a copy of the report for the first time.
Its director of railway safety Ian Prosser said he was "extremely disappointed" that the document had only come to light now.
He said: "I am very concerned about companies not providing important information to a safety investigation."
An official from the Rail Accident Investigation Branch (RAIB) said it did not believe the inclusion of the report would have changed its conclusion or recommendations.
A spokesman said: "This document was not known to the RAIB and is therefore an item of new evidence.
"Had this document been made available to the RAIB it is likely that reference would have made to it in our final report.
"I judge it unlikely that our conclusions or recommendations would have been significantly different."
A statement from Network Rail said: "The deaths of Olivia Bazlinton and Charlotte Thompson over five years ago, were a tragedy.
"It was also an accident, as the coroner's verdict clearly stated. The thoughts of Network Rail remain with the girls' families and friends.
"Every accidental death at a level crossing is tragic. Fortunately they are rare and Britain has a safety record that stands up well to international comparisons.
"Just this week Network Rail unveiled more measures to deter incidents at level crossings.
"Our awareness campaign began over six years ago and was commended by the coroner at Olivia and Charlotte's inquest."