The BBC's Reeta Chakrabarti: Doreen Lawrence asks the government to act decisively

In Channel 4's Alternative Christmas Message, to be broadcast on Christmas Day, Doreen and Neville Lawrence say the inquiry chaired by Sir William McPherson provides an opportunity for real change that must not be squandered.

Stephen Lawrence: No one has been successfully prosecuted for his murder

The white racists who murdered 18-year-old Stephen in 1993 have never been successfully prosecuted.

Evidence given at the inquiry revealed a series of Metropolitan Police blunders in attempting to bring them to justice.

Mr and Mrs Lawrence's Christmas broadcast, made at the invitation of Channel 4, is both an expression of deep personal grief at the loss of their son, and a public challenge to the government to transform British policing.

Neville Lawrence: Stephen's death must not be in vain

Neville Lawrence calls on senior police officers to weed out racist colleagues so public confidence, badly dented by the inquiry, can be restored.

But he says the public must be allowed to scrutinise any reforms.

He says: "Any recommendation that comes from the inquiry has to be monitored so we know exactly what's happening and at the end of the day we'll see what these people are doing to make sure racists who go out and kill people don't get away with it.

"If we lose this opportunity it will be like my son has died in vain."

Doreen Lawrence: The inquiry has given us the opportunity for real change

Doreen Lawrence says she suffered pain during the public inquiry, listening to evidence from the men she believes murdered her son.

But the inquiry was also a triumph, she says, in that it allowed the white community to see what they have suffered.

She says it is a great honour to be able to address the country on Christmas Day - but that she would give it all up to see Stephen's face again, and to hold and embrace him.

She says: "The inquiry has given us the opportunity for real change.

"What I'd like to see is for the government not to pay just lip service as the previous government did, but to take this opportunity to have in place laws against racist murder and racist crimes - laws to help our children to walk the streets safely."

Past Channel 4 Christmas day broadcasts - which are aired at the same time as The Queen's message to Britain and the Commonwealth - have included contributions from Quentin Crisp and Brigitte Bardot.