A soundproofed torture chamber suspected to have been used by a violent drugs gang should be used to remind cocaine users of the consequences of their habits, a Dutch public prosecutor has said.

Koos Plooij told an Amsterdam court that the brutality was a “repulsive, but apparently unavoidable” reverberation of the growing use of illegal drugs in the Netherlands and neighbouring countries.

He said: “The question is how many people are willing to admit that there is indeed a connection between their cocaine use – whether it is to party, deal with work stress or suppress psychological problems.”

The protestors comments were made at the trial of 11 suspects, who are accused of planning use the “hell-like” torture chamber to torture rival gang members.

Police made the discovery two years ago in Wouwse Plantage, south of Rotterdam, after French officers cracked encrypted phones being used by criminals. Police said the seven shipping containers, converted into cells and torture chambers, were found before they were used.

Six of the containers, fitted with handcuffs and legcuffs, were allegedly to be used as holding cells. While the seventh was fitted with a dentist’s chair and apparent torture weapons, such as scalpels, claw hammers, pliers, pruning shears and gas burners.

Officers also discovered a freezer large enough to hold more than one person and a mixing tub allegedly set to be used to waterboard the gang’s victims.

During the hearing, prosecutors presented messages, intercepted by the police operation, from the alleged ringleader known as Roger “Piet Costa” P. “There are a few now and I hope I get the chance to torture them,” he allegedly wrote.

A second man, who is terminally ill and not currently on trial, allegedly wrote: “If they don’t cooperate, right in the knee.”

Prosecutors called for Roger P to be jailed for 12 years. The alleged kingpin is already facing a prison sentence of 17 years and nine months for a separate conviction.

The suspects deny the charges.