The family of Giulio Regeni, the Italian doctoral student who was murdered in Egypt in 2016, are demanding that Rome withdraw its ambassador to Cairo for a second time in response to what they say is Egyptian pressure on their lawyers and efforts to prevent investigation into their son’s death.

“Enough is enough,” Paola and Claudio Regeni said in a joint statement with their lawyer, Alessandra Ballerini. “The withdrawal of the Italian ambassador from Cairo can no longer be postponed.”

Italy recalled its ambassador in April 2016 in objection to Egypt’s unwillingness to cooperate with an investigation into the murder of the 28-year-old.

Regeni’s mutilated body was found on an outlying Cairo desert highway in February that year, eight days after he disappeared while researching trade unions in Egypt. An Italian autopsy found his corpse bore the hallmarks of torture, and there were widespread suspicions that Egyptian officials were responsible.

An Italian ambassador returned to Egypt in August 2017 in an effort to “reinforce judicial cooperation and as a consequence the search for the truth,” according to the then foreign minister, Angelino Alfano.

But in the two years since, Italian officials have accused their Egyptian counterparts of impeding their investigation and of failing to provide vital evidence that could show how Regeni disappeared and who was responsible for his death. The Regeni family and Ballerini said the Egyptian authorities were instead focused on intimidating their legal team in Cairo.

“This is an outrageous and disturbing attitude,” the statement said. “At this point the only possible step is to withdraw the ambassador.”

A spokesman for the Egyptian ministry of foreign affairs repeatedly declined to respond when contacted by the Guardian to ask about the Regenis’ comments.

Maha Ahmed, of the Cairo-based Egyptian Commission for Rights and Freedoms, is under investigation and risks imprisonment, according to the ECRF. The commission tracks enforced disappearances like Regeni’s, while some of their employees act as the Regeni family’s Egyptian legal counsel.

“With Maha, they are repeating the same scenario as Amal Fathy,” said Mohammed Lotfy, the executive director of ECRF. Lotfy’s wife, Amal Fathy, was arrested during a dawn raid at their home last May and imprisoned until December, accused of a range of charges including “spreading false news” and membership of a terrorist group.

Lotfy and the ECRF believe the Egyptian authorities are seeking to prevent them from working on the Regeni case by intimidating ECRF employees and their family members. “I think the message is clear: take your hands off the case or else you’ll get hurt,” said Lotfy, adding that Ahmed’s husband, Mohammed Helw, was one of the ECRF lawyers granted power of attorney by the Regeni family.

An ECRF researcher, Ibrahim Ezz El Din, was forcibly disappeared a week ago. A team headed by Sherif Magdy Abdel Al, an Egyptian National Security Agency official, arrested a second lawyer, Haitham Mohamedeen, on 13 May. Abdel Al is one of five Egyptian NSA members named by Italian prosecutors last November as suspects in Regeni’s disappearance.

Italian officials are continuing to maintain pressure on Egypt. “Giulio’s parents will not be alone,” wrote the Ppresident of the Italian parliament, Roberto Fico, in a statement on Facebook. “Next week we will talk about Giulio with the German Bundestag: Giulio was not in fact just an Italian researcher, but a European one. It is a matter that concerns and must concern all the countries of the union.”

Italian prosecutors confirmed they had requested further evidence from their Egyptian counterparts after a new witness came forward testifying that one of the five accused men was overheard discussing Regeni’s kidnapping at an African security conference in 2017.

The Rome prosecutor Sergio Colaiocco, who is leading the investigation into Regeni’s murder, said: “We have sent the authorities in Cairo an international rogatory [letter of request]. We can’t disclose its contents. But we can say that our request is related to the new witness and that we’ve had no answer since then.”

The ECRF believes that the Egyptian authorities are unwilling to shed light on Regeni’s case owing to what it could reveal about the widespread practice of enforced disappearances in the country, where civilians are covertly arrested without legal representation or access to their families. The ECRF documented 230 cases of enforced disappearances between August 2017 and September last year.

“The authorities say there are no enforced disappearances in Egypt,” said Lotfy. “Yet while we are working on the case of a forcibly disappeared Italian researcher in Egypt, they forcibly disappear one of our staff members working on one of the most important cases,” he said. “They’re unafraid of public opinion. They want the world to believe what cannot be believed.”