Prosecutors said today the investigation into the death of Wpc Yvonne Fletcher was "still ongoing" despite a claim that there was enough evidence to charge two Libyan men in connection with the killing.
A review of the case by the Crown Prosecution Service (CPS) reportedly found that the men played an instrumental role in organising the shooting which killed the 25-year-old as she policed a demonstration at the Libyan embassy in central London in 1984.
The Daily Telegraph said that the leaked document identifying the two men was ready in April 2007, weeks before a meeting between former prime minister Tony Blair and Colonel Muammar Gaddafi opened trade links between the two countries.
A spokeswoman for the Crown Prosecution Service said: "The investigation into the death of Yvonne Fletcher is ongoing and there is still evidence to be gathered.
"So the CPS has yet to receive a file containing the admissible evidence from a completed investigation. It would only be at that point that we could give final advice on prosecution."
She added: "The police sought further advice in relation to their ongoing investigation from the CPS in 2007 and interim advice was provided.
"This advice was accompanied by a letter which said, 'Whilst I have offered a view (in the interim advice) that a matter of this nature might be capable of proceeding, some of the evidence should be revisited to determine whether it is still available. In addition, there may be some additional avenues of investigation which might be appropriate to consider'.
"These further investigations still continue. Any public revelation of any details of this investigation could jeopardise the gathering of this further evidence."
The Telegraph reported that the CPS had found that neither of the men referred to in the report had diplomatic immunity, but were thought to have escaped from the building moments before it was surrounded by police in an 11-day siege.
It is also said to name the man who fired the shot that killed Wpc Fletcher but concluded there was not enough evidence to bring a murder charge against anyone.
The report apparently states that the killers were under orders from a group of Gaddafi loyalists who planned to "punish" demonstrators with violent attacks.
Wpc Fletcher's mother, Queenie Fletcher, told the newspaper: "If there is enough evidence to prosecute these two men, they should face trial in a neutral country."
Earlier this year officials said the Scotland Yard investigation into the killing had stalled when Tripoli suspended co-operation.
Gordon Brown raised the matter with Col Gaddafi when they met at the G20 in July.
A spokeswoman for the Metropolitan Police said: "The murder investigation has always remained open and the Met remains committed to finding the people responsible. Detectives remains in regular contact with Wpc Fletcher's family and update them on developments."