The Netherlands was in shock on Wednesday after its usually discreet international drugs underworld – worth more than €20 billion a year – seemingly burst into the open with the assassination of a top lawyer and part-time judge in front of his wife as he left for work.

Derk Wiersum (44), a specialist in organised crime cases and a partner in a major Amsterdam law firm, was saying goodbye on his doorstep in the suburb of Buitenveldert just after 7.30am when he was approached by a gunman who shot him several times before escaping on foot.

The killer was described as between 16 and 20 and dressed in black.

Prime minister Mark Rutte, who was briefed on the case as he arrived at his parliamentary office in The Hague, said he was “extremely disturbed” by the killing – which it now appears could be linked to the Netherlands’s most wanted criminal.

The mayor of Amsterdam, Femke Halsema, called an immediate meeting of police chiefs and justice officials, and later the government said it had also taken the highly unusual step of calling in the office of the National Counterterrorism and Security Co-ordinator.

Mr Rutte and his government did not escape criticism, however. Jan Struijs, leader of the largest police union, the NPB, described the “liquidation” of Mr Wiersum as “an attack on the rule of law”, adding: “This is confirmation, if it were needed, that we are all living in a narco-state.”

‘Parallel economy’

The NPB has long argued that the failure of successive governments to provide adequate funding for police combatting drugs gangs has led to the development of a “parallel criminal economy” which “permeates all corners of life” in the Netherlands – and believes it cannot be challenged.

There was also criticism of the fact that Mr Wiersum – who had frequently argued for better protection for prosecution witnesses in gangland cases – had no protection himself, apart from “a few technical measures” at his home, where he lived with his wife and two children.

The working hypothesis is that the killing is linked to the high-profile gangland case in which Mr Wiersum was involved, in which 16 men are accused of five drugs-related murders and one attempted murder in Amsterdam and Utrecht between 2015 and 2017.

The prime suspect in that case is 41-year-old Ridouan Taghi – the Netherlands’s most wanted criminal – who remains at large.

Mr Wiersum was representing one of the 16 accused, Nabil Bakkali (31), who had agreed to give evidence for the prosecution when the case comes to trial in 2020.

Mr Bakkali’s brother Reduan, who had no involvement in the case, was shot dead last year – shortly after the justice department revealed that Nabil Bakkali had become a prosecution witness.