Doreen plans for 20th year of son's death

Ms Lawrence, who founded the Stephen Lawrence Charitable Trust, said: "Our focus has to be on the next 20 years. There is more to be done to get justice for Stephen and to ensure that no other family has to go through what we endured."

A memorial service will be held at St Martin in the Fields church in central London on April 22, the date Stephen died in 1993.

A concert planned for April, a criminal justice lecture, an annual memorial lecture and a gala ball will help raise awareness and funds for the campaign.

Ms Lawrence also reflected on the conviction of Gary Dobson and David Norris this time last year who were jailed for life for Mr Lawrence's murder.

"This time last year we faced the conviction of two of Stephen's killers and the relief I felt then has stayed with me through the extraordinary year that was 2012."

During the trial, the court heard a gang of five or six white youths set upon the A-level student in Eltham, south-east London.

At the trial judge Mr Justice Treacy described the murder as a "terrible and evil crime" that had been committed "for no other reason than racial hatred."

He urged police not to "close the file" on catching the rest of Mr Lawrence's killers and Ms Lawrence continues to press for the tracing and arrest of others involved in the murder.

The Metropolitan Police faced fierce criticism of the original investigation into Mr Lawrence's death.

A public inquiry branded the force institutionally racist and claims were made by Mr and Mrs Lawrence's lawyers that some officers were influenced by Mr Norris's former drugs baron father.

The breakthrough in the investigation came when a cold case team of forensic scientists found tiny traces of blood, hair and fibres on clothing seized from Mr Dobson and Mr Norris's homes.