Video report by ITV News Correspondent Juliet Bremner
Stephen Lawrence's mother said she will "never" give up trying to find her son's killers after the Metropolitan Police announced their investigation into the 18-year-old's death was now "inactive".
In a statement, Baroness Lawrence said the Metropolitan Police had "given up" trying to find those responsible for the racist attack on her son at a south-east London bus stop in 1993.
Two men had been convicted of Mr Lawrence's death in 2012 but Ms Dick said there were no further lines of inquiry.
In a statement, Baroness Lawrence said: "Eight years after the conviction of two of the men that murdered Stephen I am now told that there are no further leads to follow in the investigation.
ITV News correspondent Juliet Bremner reports from Scotland Yard
"I am truly disappointed that those others who were equally responsible for my son's racist killing may not be brought to justice."
She added: "I am very sad that a line has now been drawn into the investigation and that it is now in an 'inactive' phase. Despite this, I would still urge anyone who has any information that could help me get all of Stephen's killers convicted, to come forward. "It is never too late to give a mother justice for the murder of her son. Whilst the Metropolitan Police have given up, I never will."
Stephen's father, Neville Lawrence, said he was "disappointed... but not surprised" at the Met Police decision.
In a statement, Mr Lawrence said: "I am disappointed to hear this news but not surprised. I had hoped that the conviction of two of the killers in 2012 would lead to new evidence coming to light and a prosecution of the other suspects. "This has unfortunately not happened and, over the last few years, I have had to come to terms with the reality that some of the killers of Stephen may never be brought to justice for what they did."
He added: "Stephen died 27 years ago in a senseless murder by racists. The tragedy of this for us was compounded by the initial police response and investigation which were tainted by racism and incompetence. The police failures meant that we as a family had to fight a system as well as deal with the grief of losing our son.
"With the announcement today that the investigation has become inactive, I am conscious that the case can never be closed for me. I will always live with the hope that someone might come forward with evidence which will allow us to achieve full justice for Stephen - by bringing about the prosecution of the others responsible for his murder."
Ms Dick said it was a "matter of huge regret" the murderers of the teenager had not been caught.
"There are still people out there who were part of the horrible, horrible racist murder," Dame Cressida said.
She added: "We've come to the view right now that there are no viable lines to the enquiry, we've been working very closely with the Crown Prosecution Service and people independent to the investigation have had a look to assure me that nothing more can be done at the moment."
Ms Dick added: "The investigation has now moved to an ‘inactive’ phase, but I have given Stephen’s family the assurance that we will continue to deal with any new information that comes to light."
When asked about how she broke the news to the family of Stephen Lawrence, Ms Dick said: "It's a matter of huge regret to me that there are still people out there who were part of that horrible, horrible, racist murder of Stephen Lawrence."
Ms Dick added she is "convinced that there are people who could be brought to justice".
Twenty-seven years ago, the black teenager was murdered while waiting for a bus in south London.
Mr Lawrence was stabbed to death by a group of up to six white men in an unprovoked racist attack as he waited at a bus stop in Well Hall Road with a friend.
His murder, the court case and the failings of the Metropolitan Police captured the nation's attention.
Now, the Metropolitan Police has confirmed they have completed all identified lines of enquiry from the murder in 1993.
So far the Met Police has convicted two people in 2012, but Ms Dick said there are "still people free and if in the future new information comes to light or new technology allows us to go back and look at the investigation again as we have done in the last few years then of course we will take that opportunity."
In January 2012, Gary Dobson and David Norris were found guilty of being involved in the attack on Mr Lawrence, and sentenced to life imprisonment.
Two of the three remaining suspects, brothers Neil and Jamie Acourt, have since served jail time for drug dealing, while Luke Knight has remained free.
Ms Dick said: "We have been extraordinarily committed to this investigation, it's a set of investigations like no other, in scale and complexity and I do regret that we have not got to the stage where all the people involved in that dreadful attack have been brought to justice and I recognise that mistakes were made so in the early days."
"I am convinced that there are people who could be brought to justice."
She added: "We have two people that have been convicted and throughout all the investigations and indeed reviews by judges, including Sir William MacPherson, there has been an understanding that four, five, or six people were involved in this attack were murders, so there are people who are still to be brought to justice."