No individuals will face charges over the 1999 Ladbroke Grove rail crash which claimed 31 lives.
The crash at Ladbroke Grove, near Paddington, killed 31 people
The Crown Prosecution Service (CPS) said there was "insufficient evidence" to provide a realistic prospect of conviction" of any individuals.
But it said the company Network Rail (formerly Railtrack) would face criminal charges under the Health and Safety at Work Act 1974.
The Paddington Survivors Group said it "eagerly awaited" the result of this.
More than 400 people were injured in the two-train crash on 5 October, 1999.
The Paddington Survivors Group chairman Jonathan Duckworth, a who was among passengers in the Great Western train injured, said he was "not particularly surprised" at the CPS ruling.
"It was something we were expecting after other cases had failed," he said.
"We eagerly await the result of the prosecution to be brought under the Health and Safety at Work Act. We think the best way forward is to impose very large financial penalties on companies."
CPS principal legal adviser Chris Newell said: "I know this decision will come as a bitter disappointment to those left bereaved and seriously injured as a result of the Ladbroke Grove collision.
"But the CPS is bound to follow the tests set out in the code for crown prosecutors and to apply the law in the way in which it is interpreted by the courts."
He added that he had offered to meet people "directly affected by this tragedy" to further explain the reasons behind the decisions.
Louise Christian, the lawyer for many of the families of the people killed in the disaster, told BBC News this was a devastating decision for the bereaved and accused the CPS of losing its nerve.
She said: "I think that the reason this decision has been taken is because of the judgement of the judge in the Hatfield case, which was on the particular facts of that case that that prosecution didn't succeed, but the CPS has now had a failure of nerve and has decided that it would be criticised if it brings another unsuccessful prosecution."
The crash happened when a Thames Trains train driven by Michael Hodder, 31, went through a red signal and hit a London-bound Great Western express.
Thames Trains and Railtrack were both criticised in a public inquiry report by Lord Cullen.
Thames Trains pleaded guilty to health and safety offences in relation to the 1999 crash and was fined £2m in April 2004.