The mayors of Amsterdam and Rotterdam have urged the government to step up its efforts to tackle organised crime, warning of ‘a criminal culture of violence that is acquiring Italian features.’

In a joint letter to parliament, Femke Halsema and Ahmed Aboutaleb said the drugs trade and money laundering operations were increasing the wealth and power of the underworld, with violent consequences.

The murders of journalist Peter R. de Vries and lawyer Derk Wiersum, both of whom were advisers to a key witness in the ongoing ‘Marengo’ trial, were described at the time as an ‘attack on the legal system.’ Suspected gang leader Ridouan Taghi and 16 associates are accused of ordering 13 murders, six of which were carried out in a 15-month period.

‘Journalists, lawyers, politicians and people with a public function are having to be protected, houses are being shot at and attacks are being carried out,’ they wrote.

‘It’s not just about conflicts erupting over control of the drugs trade, but we are also seeing violence as a display of power and with the intention of weakening our democratic legal system.’

The reference to the mafia comes in the same week that justice minister Dilan Yesilgöz and Franc Weerwind travelled to Italy to study the measures taken to combat organised crime since the murder of two judges 30 years ago.

In Italy suspected mafiosi are covered by a section of the penal code known as 416-bis, which allows the authorities to impose strict monitoring rules in prison to effectively cut off contact with the outside world.

‘I’m impressed with how the Italians deal with external communication,’ Weerwind said. ‘They cut off all connections so that it is totally impossible for criminals to operate from inside prison.’