Former senior official Ollie Robbins took legal action in connection with the dismissal

Sir Ollie has defended his role in the process, saying the government’s vetting processes must be “absolutely confidential”.

He previously told MPs he had not seen the document from UK Security Vetting (UKSV), the government’s domestic vetting unit, which handled Lord Mandelson’s vetting review.

Instead, they said they were given a verbal explanation that the investigating agency considered Mandelson a “borderline case” but that the State Office could grant leave “subject to appropriate risk management”.

Announcing Sir Ollie’s decision to take legal action, the FDA said in a statement that the Foreign Office’s decision to fire him was a “regrettable misunderstanding” of the government’s inspection procedures.

“Instead of being under an obligation to tell ministers about the process leading up to the decision to investigate, Oli had an obligation not to,” he added. “Not only was there no fairness in his dismissal, there was no due process at all.”

The union also said it wanted to argue that Sir Kerr did not have the legal authority to sack Sir Ollie, who was the head of the UK’s diplomatic service.

In the year Sir Ollie, who will be appointed to the Foreign Office in early 2025, has held senior civil service roles and was previously the government’s lead official in Brexit negotiations with the EU.

In his statement, he stated that he was taking legal action “reluctantly” and said that “it was unnecessary if the Prime Minister only apologized for the mistakes he made and corrected the problems and losses caused to me and my family.”