A special casework lawyer from CPS London has thoroughly reviewed all the evidence in the case.
This included evidence gathered by police during the reinvestigation, papers from the private prosecution and papers from the inquest.
All the evidence from previous investigations was also studied to identify any statements or other evidence relevant to this review.
The CPS sought advice from senior counsel who reviewed the same material and came to the same conclusion as the reviewing lawyer.
A number of accounts of alleged confessions have also been investigated but almost all have proved to be second-hand hearsay and unverifiable and therefore not admissible.
None are sufficient to support a prosecution.
Claire Ward, CPS London special casework lawyer, said:
"We must apply the clear objective test, as set out in the Code for Crown Prosecutors, when looking at the evidence in every case and advising on prosecution. That is we must be satisfied that there is sufficient evidence to provide a realistic prospect of conviction against a defendant.
"To do that the evidence has to be admissible and believable.
"We have conducted a very thorough review of every item of evidence relevant to this case to establish whether it would be admissible in court and would support a prosecution.
"I have also had the benefit of looking through the papers from the private prosecution, for which I am very grateful to Mr and Mrs Lawrence.
"The police have carried out a very thorough reinvestigation. Investigating officers have followed up all additional questions senior counsel and I have put to them, provided extra material as we've requested it and conducted further investigation wherever we have suggested it.
"However, despite this, there is no reliable, admissible evidence which places any identifiable suspect at the murder scene at the time it took place.
"The sheer volume of evidence and other material relevant to the case and the importance of ensuring that the review was exhaustive has meant that it has been a lengthy process but one that we have been mindful to carry out carefully and meticulously."
The Director of Public Prosecutions, Ken Macdonald QC, said:
"I realise that Mr and Mrs Lawrence and Duwayne Brooks will have hoped for a different conclusion to the review so that someone could be prosecuted for the terrible crime that happened.
"Our policy is to prosecute racist crimes firmly and robustly wherever the evidence allows and we are fully committed to that principle.
"We all need to reflect on this dreadful murder and recognise the profound effect it has had on our national consciousness.
"However, no matter how important or serious a case is, if on the strength of the evidence it does not pass the test that we apply, it must not go ahead.
"That is the position in this case."
Doreen and Neville Lawrence and Duwayne Brooks were given a detailed explanation of the advice to police by the reviewing lawyer at meetings prior to the CPS's announcement.
The chief crown prosecutor for London, Dru Sharpling and Director of Public Prosecutions, Ken Macdonald QC, also attended the meeting, as did a number of Metropolitan Police officers.