U.N. rapporteur on extrajudicial executions Agnes Callamard told newspaper Algemeen Dagblad it was "more than disappointing" that the Dutch queen had apparently not raised the murder of journalist Jamal Khashoggi with the Saudi prince.
"It's one thing (for her) to meet this man, it's something else to remain silent," Callamard was quoting as saying.
"Your Royal Highness, when you gave MBS the honor of your meeting, I trust you raised the extrajudicial killing of Mr Khashoggi, the botched investigation, no focus on the chain of command, the closed trial. I trust you asked for #justiceforJamal," tweeted Agnes Callamard on Saturday.
Callamard, the U.N. special rapporteur on extrajudicial killings, issued a report last week that implicated the crown prince in Khashoggi's killing and called on the international community to launch a formal investigation.
Khashoggi, a Washington Post columnist and critic of the crown prince, was allegedly murdered and dismembered by Saudi operatives in the Saudi consulate in Istanbul in October 2018. His remains have never been found.
Queen Maxima met with the crown prince during a meeting of G20 nations in Osaka, Japan. Dutch media reported their talks focused on microfinance and helping women set up businesses, but that Khashoggi was not brought up.
"That is more than disappointing," Callamard told the Dutch daily Algemeen Dagblad in an interview.
"It is one thing to meet this man. It is something else to remain silent. At this point, silence equals complicity," she was quoted as saying.
"If you do not speak and do not demand justice, it suggests that you have no worries," she said.
The Dutch Royal House could not immediately be reached for comment, but local media cited a statement from the royals as confirming that the meeting had taken place. It added that it had been obligatory for the queen to meet the crown prince because Saudi Arabia will host the next G-20.
Maxima, an Argentine who married the Dutch crown prince in 2002, had addressed the G-20 in Japan about women's empowerment.
The Saudi Center for International Communication published a photo of the meeting on Twitter, saying "many topics were on the table" during their conversation.
Callamard's comments followed rare criticism of the royals by Dutch lawmakers, several of whom said they would table the matter for discussion in parliament on Monday.
"Whoever approved this conversation between Maxima and the Saudi crown prince understands nothing of diplomacy and even less about what's good public relations," Sjoerd Sjoerdsma of the centrist D-66 Party, a member of the governing coalition, said in a statement on Twitter.