The judge in the Stephen Lawrence murder trial has urged police not to "close the file" on the case as the dead teenager's father called on convicted killers Gary Dobson and David Norris to turn other suspects in.

Mr Justice Treacy made his appeal as Metropolitan Police Commissioner Bernard Hogan-Howe said that the remaining culprits "should not rest easily in their beds".

Gary Dobson, 36, and David Norris, 35, received life sentences at the Old Bailey today for the racist murder of Mr Lawrence nearly 19 years ago.

Dobson, who is already serving a five-year sentence for drug-dealing, was sentenced to at least 15 years and two months while Norris was given a minimum of 14 years and three months for the murder, which the judge said was a "terrible and evil crime".

It is understood that police plan to meet next week to assess where the case stands.

In court, Mr Justice Treacy called forward Detective Chief Inspector Clive Driscoll, who has been the senior officer in the case for a number of years.

He told him that the public inquiry into the circumstances surrounding Mr Lawrence's death had "shamed and humbled" the Met, but praised the hard work done in recent years.

The judge went on: "At least a measure of justice has been achieved at last. However, the convictions of Gary Dobson and David Norris will not, I hope, close the file on this murder. On the evidence before the court, there are still three or four other killers of Stephen Lawrence at large.

"Just as advances in science have brought two people to justice, I hope the Metropolitan Police will be alert to future lines of inquiry, not only based on developments in science but perhaps also information from those who have been silent so far, wherever they may be."

Earlier, he had sentenced Dobson and Norris in a packed but silent courtroom, saying that the murder was committed "for no other reason than racial hatred" and condemning the pair for showing "no remorse" over their crime and for lying in court.

Mr Justice Treacy told the pair: "A totally innocent 18-year-old youth on the threshold of a promising life was brutally cut down in the street in front of eyewitnesses by a racist, thuggish gang.

The evidence in the trial could not prove who wielded the knife, but he said that whoever used it had done so with Dobson and Norris's "knowledge and approval".

"You were both members of that gang. I have no doubt at all that you fully subscribed to its views and attitudes."

When it was over, Dobson left speedily, stepping over Norris who had bent down to pick up his papers.

Norris then kissed his hand and offered it up to the public gallery in a thumbs-up sign before he too was led from the court.

As the judge rose to leave, a few people began clapping in the public gallery.

Dobson's father, Stephen, called down to the court: "Shame on all of you."

It is understood that a decision will be made on whether to keep the men at Belmarsh prison, in south east London, where Norris has previously been beaten up.

After sentencing, the Press Association reported that Neville Lawrence said the sentencing of Gary Dobson and David Norris was "only one step in a long, long journey" and called for the other killers to be brought to justice as well.

Addressing reporters outside the Old Bailey, he said: "One of my greatest hopes is that these people have now realised that they have been found out, and they are now going to go and lie down in their beds and think that they were the whole ones who were responsible for the death of my son.

"And they are going to give up the rest of the people so that I (can) come out here again in a year's time and talk to you people again."

Meanwhile, Stephen's mother, Doreen, said it had been a "really difficult day" but added that she could now start moving on with her life.

She thanked the judge, accepting that he was unable to pass stiffer sentences on Dobson and Norris.

"The sentences that happened may be quite low, but at the same time the judge's hands were tied. And for that, as much as he can do, I am very grateful," Mrs Lawrence said outside court.

"It's the beginning of starting a new life because we've been in limbo for so long. So today we're going to start moving on, and it's time to take control of my life once more."