Prosecutors in the Netherlands have requested flight-data recorder and cockpit-voice transcripts from the crashed Turkish Airlines Boeing 737-800 at Amsterdam Schiphol.
The Openbaar Ministerie says the Dutch Safety Board does not have to grant the request, contained in a letter from its aviation department, because the prosecutor is "lacking" a legal basis. But it adds that it has submitted the letter because the data can give "an insight into the circumstances of the accident".
"We are awaiting a response from the Safety Board," says the prosecutor's office.
Judicial intrusion into accident investigation has attracted high-profile criticism over the last few days, after the Italian Agenzia Nationale per la Sicurezza del Volo sought "decisive action" to avoid the "problem of conflict" between investigators' needs and the rules of criminal proceedings.
ANSV has accused judicial authorities of hampering the investigation into the fatal 7 February crash of a Cessna 650 executive jet in a suburb of Rome. It says the inquiry has "come to a standstill" after the seizure of crucial material, including the flight recorders and relevant "vital" documentation, by legal officials.
The Italian agency adds that the US National Transportation Safety Board has requested a copy of data on the recorders but that, as a result of the development, ANSV has been unable to provide the information.
Cockpit crew representatives are supporting the ANSV's stance, and backing calls for a change in Italian law to give technical investigation priority over judicial inquiries.
"Under present legislation the judicial inquiry takes precedence," says the International Federation of Air Line Pilots' Associations.
Absence of data from the flight-data and cockpit-voice recorders from the Cessna jet will "seriously impact the effectiveness and speed" of the investigation, it adds.
Prosecutors have also "interfered" with French inquiries into last November's fatal Airbus A320 crash in the Mediterranean Sea, claims the Flight Safety Foundation. "In recent days the French authorities have returned some of the Airbus evidence to safety investigators," it states.
Chief executive William Voss says he understands the demand for justice and accountability. But he adds: "We cannot allow the safety of the aviation system to be jeopardised by prosecutorial overreach.
"Unless there is evidence of sabotage, law enforcement and judicial authorities need to step aside, allow accident investigators immediate access to the wreckage and to surviving crew and passengers, and let safety professionals do their job."