Britain's attorney general will not refer the sentences of Stephen Lawrence's murderers to the appeal courts for being too lenient.

Gary Dobson, 36, and David Norris, 35, were sentenced to 15 years and two months and 14 years and three months respectively for the 1993 racist murder of Lawrence.

The sentences were considered lenient by the parents and many observers but the judge's hands were tied by the fact that the two men were under the age of 18 at the time of the murder.

This meant Justice Treacy, who presided over Dobson and Norris's trial, could only hand out juvenile sentences.

He acknowledged the sentences would be "lower than some might expect".

"This was a despicable and appalling crime. Justice was long delayed and I can fully understand why some people are unhappy that the minimum terms handed down were not longer," Dominic Grieve, attorney general, said.

"However, having considered the sentences carefully I have come to the conclusion that the minimum terms are within the appropriate range of sentences, bearing in mind the offenders' ages at the time of the crime, and therefore I have decided not to refer them to the court of appeal.

"It is worth emphasising that the terms are the minimum periods that will be served. Dobson and Norris will not be released unless and until the Parole Board considers they do not pose a risk."

Under section 36 of the Criminal Justice Act 1988 the attorney general has the power to refer sentences to the Court of Appeal if they are deemed "unduly lenient".

Stephen Lawrence was stabbed to death in a racist attack at a south London bus stop in April 1993.