Two of Britain’s most notorious rapists should never be released from prison, the court of appeal has heard.

Lawyers argued on Wednesday that the serial rapists Reynhard Sinaga, 37, and Joseph McCann, 35, should receive whole-life terms after causing an “ocean of harm”. The “long-term mental suffering” of victims meant their crimes should be regarded as possibly more harmful than other serious, violent offences.

Both men were originally given minimum terms of 30 years, meaning they are eligible for parole after serving that period.

The most senior judges in England and Wales heard how Sinaga, a post-graduate student from Indonesia, was convicted in four trials of drugging and raping 48 young men he had lured to his Manchester flat under the guise of a “good Samaritan”.

Afterwards, Greater Manchester police said they had evidence he had assaulted at least 195 men, making him Britain’s most prolific rapist. He had filmed the attacks and kept “souvenirs” from his victims: wallets, watches and mobile phones.

In December last year, McCann, from London, was convicted of all 37 counts relating to a fortnight-long rampage in 2019 that stretched from London to Cheshire. He raped eight victims, including a 71-year-old woman and a boy aged 11. The boy and his teenage sister were attacked in front of each other in their own home.

Michael Ellis QC, the solicitor general, acting for the government, said McCann “degraded, humiliated and terrified” his victims.

“The effect on these victims was profound, they suffered severe psychological damage; distressing memories; permanent, life changing effects; and a genuine, but of course irrational, sense of guilt,” Ellis told judges including the lord chief Justice of England and Wales. “These offences are among the most serious sexual offences ever seen in this court.”

Both men’s cases were referred to the court of appeal by the attorney general’s office under the “unduly lenient sentencing” scheme.

Until now, whole-life prisoners have always committed exceptionally brutal murders, including the killing of children or involving a sexual or sadistic nature or extremist ideology, the court heard.

About 50 prisoners are subject to such sentences, including Michael Adebolajo, who murdered the soldier Lee Rigby near his barracks in London, and the serial killer Levi Bellfield.

Sarah Whitehouse QC, for the Crown Prosecution Service, told the appeal judges that just because none of McCann and Sinaga’s victims died it did not mean the men should automatically be spared full-life terms.

She said: “It is not right to compare the facts of one case with another. It is rarely helpful and indeed it is odious to seek to compare the harm caused in these two cases with, for example, the murder of a child or the murders of multiple victims.

“But we observe that harm is not limited to physical harm. As increasingly more is known about the psychological effects of sexual offending, particularly the long term effects, we invite the court to consider the long term mental suffering inflicted on the victims in these two cases.

“Such suffering is not as dramatic or obvious as the broken jaw or the knife wound across the face or the broken nose. It is often invisible. But in our submission must be given an equal place, if not a higher place, in the hierarchy of harm. In both cases brought today to the courts there is what could be described a vast ocean of harm.”

Whitehouse noted that one of Sinaga’s victims had tried to kill himself, others had suicidal thoughts and some were now abusing drugs and alcohol.

However, the rapists’ lawyers argued that their original sentences should stand, noting that neither men would be automatically released when they had served their minimum term.

Richard Littler QC, for Sinaga, said that taken individually, his client’s crimes were not “exceptionally serious”. But that they became so when all added together.

He said: “The whole life sentence has always been classified as the sentence of last resort. We submit in this case it would not be appropriate on the facts. There’s no authority which would justify the imposition of a whole life sentence where the individual facts themselves are not exceptionally serious, but because there are so many complainants, the prolific offending makes the case exceptional.”

The appeal court judges will give judgment on Thursday at the earliest.