Our letter on the Mandelson scandal

Prime Minister's Office

10 Downing Street

20th April 2026

Dear Prime Minister,

The public deserves to know exactly what happened when Mandelson was appointed as US Ambassador despite failing the required security vetting. This is especially serious given that you told Parliament the correct process had been followed. 

Please will you ask your Independent Adviser on Ministerial Standards, Sir Laurie Magnus, to launch an investigation into Mandelson's appointment?

In March, Sir Laurie refused to do so because ‘the relevant process for a political appointee has been followed’. That reasoning no longer stands now we know that Mandelson failed the security vetting that formed part of that process. 

We are also concerned about the apparent delay between you finding out the truth on Tuesday last week, yet making no public statement until after the Guardian broke the story on Thursday

And finally, please instruct the Civil Service to release all the documents relating to the appointment of Mandelson as US Ambassador, without delay.

Failure to do so would seriously damage the public’s trust in your government. 

Yours sincerely,

Tom Brake

CEO

Unlock Democracy