Two of Britain's “worst and most violent rapists” should die in jail instead of facing potential release, a court has been told.
Both men were given life sentences with minimum prison terms of 30 years, after which they will be considered for potential release.
Sinaga was convicted of more than 150 offences against 48 men, including 136 counts of rape, although police have linked him to more than 190 potential victims.
Michael Ellis QC described him as “the most prolific sex offender the courts have ever seen” at Wednesday’s hearing.
McCann, 35, was handed 33 life sentences for a string of abductions and sex attacks against 11 women and children, including an 11-year-old boy, during a two-week rampage across England last year.
Mr Ellis said his catalogue of offending was of the “utmost gravity” and included the use of violence and a “desire to humiliate and degrade his victims”.
Addressing five senior judges, including the lord chief justice, he said McCann’s abuse had a profound effect on his victims, who have suffered “severe psychological damage”.
“These offences are among the most serious sexual offences ever seen in our courts,” Mr Ellis added.
He said their crimes were among “some of the worst and most violent that this country has ever witnessed”.
The solicitor general argued that a whole life term would be a “proper reflection” of their crimes and the significant harm caused to a large number of victims.
The rare sentences have previously been used for the most serious killers, including the Moors murderers Ian Brady and Myra Hindley, serial killer Harold Shipman, Yorkshire ripper Peter Sutcliffe and one of Lee Rigby’s killers.
But Mr Ellis argued that whole life orders could also be applied to rape, and there was “no hierarchy of seriousness, such that homicide must always rank above sexual offending“ for sentencing judges.
He said that if the Court of Appeal does not consider that whole life terms should be imposed, then the 30-year minimum terms handed to McCann and Sinaga should be increased.
Speaking outside court, Mr Ellis said the case would set a new legal precedent if whole life terms are used.
“We have never before had a case which has resulted in a whole life sentence which was not one of homicide,” he added.
“This would be a first but it is right in my view that these cases are considered as wholly exceptional.
“This is a case where the court is minded to hear the circumstances and the legal arguments to see whether a new precedent can be created for cases of this exceptional gravity.”
Lawyers representing McCann and Sinaga argued that despite the extremely serious nature of the pair's crimes, they could not be considered “on an equal footing with the very worst cases of murder.
”Jo Sidhu QC, for McCann, said it was “perfectly conceivable” that he will never be released from prison under his current life term if he is still considered dangerous, but that it will be for the Parole Board to determine at the conclusion of his minimum term.
McCann sparked a nationwide manhunt as he launched a rampage across London, Hertfordshire and northwest England in April and May 2019.
He attacked victims aged between 11 and 71 in what police described as an “unprecedented” campaign of rape, kidnap and false imprisonment.
In some cases, McCann snatched women off the street and threatened them with a knife, while in others he used false pretences to lure victims into his car.
The rapist had been freed from prison by mistake in February 2019, and police arrested the wrong man as a suspect for one of his attacks as he remained on the run. He was jailed in December.
A month later, Sinaga was sentenced for 159 offences against 48 men who were lured to his Manchester flat, drugged and raped.
A judge said the full scale of the 37-year-old’s “perverted” crimes may never be known because some of his victims cannot remember their ordeal.
Police have counted almost 200 victims from videos that Sinaga took of himself carrying out the assaults while they were unconscious, and could not rule out others.
The Indonesian student prowled Manchester clubs looking for drunk young men, posing as a good samaritan, offering them a place to sleep or more drink.
Sinaga is thought to have laced alcoholic drinks with a drug such as GHB, known as liquid ecstasy, to incapacitate them before carrying out the attacks.
He was caught after one of the men regained consciousness and fought him off, before taking his phone to the police. The attorney general's office referred the sentences handed to McCann and Sinaga to the Court of Appeal as “unduly lenient” earlier this year and judges will be considering arguments over two days of hearings. They are expected to give their judgment at a later date.