The driver of a police patrol vehicle which was following a stolen car when it crashed, killing five teenagers, will not face any criminal action.
The fatal car crash has been under investigation since October
The Crown Prosecution Service (CPS) said a review of the case had shown there was "insufficient evidence" for charges to be made against the officer.
Five youngsters aged between 14 and 17 died in the accident in St Leonards, East Sussex, in October last year.
A full inquest is still due to be held into their deaths.
The victims were Kelly Goring, 17, Daniel Carwardine and Danielle Martin, both 16, Barrie Mackay, 15, and Lee Morgan, 14.
The CPS said in a statement: "We have taken the utmost care to ensure that all aspects have been considered in respect of this case.
Five teenagers were killed when the stolen car crashed
"It was reviewed continuously at a senior level in line with the Code for Crown Prosecutors and the conclusion was reached that there was insufficient evidence for any criminal charges.
"We understand it may be difficult for the victim's families to come to terms with this decision, but no matter how serious or important a case is it cannot go ahead if there is not a realistic prospect of conviction."
The five teenagers were in a stolen car that was spotted by a marked police vehicle in the early hours of 29 October.
It collided with three walls, a lamppost and a parked car in Battle Road, St Leonards.
Lee Morgan's father Gerry said on Friday he was angry investigations were still ongoing nearly seven months after his son's death.
"I think it's disgusting because everything's been dragging on," he said. "You can't make plans and you just don't know what to do."
Mr and Mrs Morgan have criticised the length of the investigation
Michael Foster, the MP for Hastings and Rye, said the victims' families were still waiting for answers.
"We don't know the evidence on which the CPS decision has been made and that really is the problem at the moment," he said.
"I've been in touch with the coroner and I know he intends as soon as he gets the police report in full to hold the inquest as soon as justice allows.
"That's the opportunity for the family to ask the questions they need answered."
An inquest date will be set once the coroner for East Sussex has received a completed report from the Independent Police Complaints Commission.
An IPCC spokeswoman said they would use the coroner's findings to "consider any misconduct or disciplinary issues as well as any lessons to be learned".