The relatives of all 19 people mobster James 'Whitey' Bulger was charged with killing should all be allowed to speak at his sentencing, federal prosecutors have argued.

The Irish American gangster, 84, was convicted in August of participating in 11 of the 19 murders he was accused of committing.

However, the Boston gangster's lawyers have argued that only relatives of the 11 victims should be allowed to make impact statements during his sentencing hearing next month.

But prosecutors have made the case that the former leader of the Winter Hill gang was convicted of two racketeering charges that required the jury to find that he was part of a criminal enterprise responsible for the murder of all the victims - regardless of whether he was the actual killer.

In court documents prosecutors wrote: "Family victims of the murder victims have a right to be heard at Bulger's sentencing."

Prosecutors also cited a recent ruling from a federal appeals court in the prosecution of Bulger's longtime girlfriend, Catherine Greig, who was convicted of helping him while he was a fugitive for 16 years.

The 1st US Circuit Court of Appeals upheld a judge's ruling to allow family members of Bulger's victims to speak at her sentencing hearing. The court found that a sentencing judge has the right to conduct a "broad inquiry" when deciding an appropriate sentence.

Assistant U.S. Attorneys Fred Wyshak Jr, Brian Kelly and Zachary Hafer wrote: "Thus, this court should exercise its broad discretion and permit all of its victims to speak at the upcoming sentencing hearing."

However, Bulger's lawyers have argued that giving the green light to relatives of the victims who he was not convicted of killing to make impact statements "trivializes the jury's function".

His attorneys said: "This court should not consider evidence of these crimes at sentencing. The court should only entertain impact statements and other evidence relating to crimes of which he has been convicted."

Until his capture in Santa Monica, California, two years ago, Bulger regularly topped the FBI's Most Wanted List.

His life of crime was depicted in the hit 2006 Martin Scorsese-directed movie, 'The Departed.'