The Detmold regional court jailed 56-year-old accused Andreas V. for 13 years, while 34-year-old Mario S. must serve 12 years.

READ ALSO: Police 'failures' probed in 'largest child abuse scandal in German history'

After their sentences, both men will be held in preventive custody, a step reserved only for the most dangerous criminals.

The pair are believed to have been the main perpetrators in a series of abuse cases that went undiscovered for years at the campsite in Lügde, around 60 kilometres from Hanover in northern Germany.

The caravan park in Lügde, sealed off by police tape. Photo: DPA

Along with a third suspect, Heiko V., they were accused of 450 instances of child sexual abuse.

Prosecutors said more than 40 children fell victim to the men at the “Eichwald” campsite between 1998 and 2018.

Most of the children were between three and 14 years old at the time.

Some 33 witnesses, including 16 victims and 12 relatives, testified before the court in the trial over the past ten weeks, many of them behind closed doors.

Outrage over the serial abuse, uncovered in late January, grew nationwide as details of failings by police and local authorities came to light.

READ ALSO: Trial begins for 'largest child abuse scandal in German history'

“Shocking cluelessness and inappropriate lack of concern about the dangers of sexual violence are widespread” in Germany, child sexual abuse commissioner Johannes-Wilhelm Rörig said in a statement.

There were 2,500 abuse investigations in North Rhine-Westphalia state alone last year, he noted.

“To effectively combat sexual abuse, we need much better cooperation between youth welfare offices, police, the judiciary, daycare, schools and the health system,” Rörig added, as well as more cash for state children's services.

He particularly urged tougher laws on child pornography, recalling that “behind every photo and every film there is real abuse of a child, often with unimaginable brutality.”