The investigations into Lord Peter Mandelson and Andrew Mountbatten-Windsor could take more than a year, the head of the Crown Prosecution Service has said.
Lord Mandelson and the former prince face questions amid controversy over their respective links to the paedophile financier Jeffrey Epstein.
Both were arrested in February on suspicion of misconduct in public office.
They were subsequently released under investigation. Both have denied wrongdoing.
Speaking about both cases on Thursday afternoon, director of public prosecutions Stephen Parkinson said: "I really don't think that anyone should expect an early resolution of the investigation.
"It wouldn't be at all surprising if it took over a year, not because of any lack of urgency, but because of the complexity, and also the international dimension is an extra factor to be considered, notwithstanding that in some cases you can get evidence back in an hour, that's not always the case, and formal procedures have to be gone through that sometimes involve courts, and that can have significant delay, so complex, time-consuming but no lack of urgency around that case."
Mr Parkinson added that the police are "responsible for investigations" but that the CPS has been "providing early investigative advice".
The update comes after the release of a second tranche of documents relating to Mandelson's appointment as UK ambassador to the United States.
The files have fuelled renewed scrutiny of the vetting process and reignited political debate about Mandelson's links to Epstein.
(c) Sky News 2026: Investigations into Mandelson and Andrew could take more than a year, CPS chief says
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