Michael Menson's relatives also want an outside force to reopen the case so the white gang thought to have attacked the 30-year-old and set him on fire are brought to justice.

In the 16 days before he died of multiple organ failure in hospital in February 1997, Mr Menson repeatedly said he had been attacked - but detectives assumed he had set fire to himself in a suicide attempt.

An inquest jury decided in September that he was unlawfully killed.

Scotland Yard later admitted senior officers had made serious mistakes in the police investigation after the family complained at its handling.

Mr Menson, the son of a Ghanaian diplomat, had musical success in the 1980s with the band Double Trouble but was later diagnosed as schizophrenic.

He was living in supported accommodation when he was found with terrible burns in Edmonton, north London.

The home secretary will be asked to set up a wide-ranging inquiry

The Police Complaints Authority (PCA) launched an inquiry into the Metropolitan Police's investigation.

The PCA inquiry was headed by Benn Gunn, the chief constable of the Cambridgeshire Constabulary.

But Mr Menson's sister, Alex, said a more wide-ranging investigation into the handling of her brother's death was required.

"What we want is something along the lines of the Stephen Lawrence inquiry," she said on Friday. "It should be a public inquiry but there has to be a parallel police inquiry."

"Given the circumstances it's screamingly obvious that would be the best way to move forward.

"I have every reason to believe that Jack Straw will take the same view."

She will meet Mr Straw with her solicitor and an official from the Ghanaian High Commission Tuesday next week.

The Home Office has declined to comment on the meeting.