Keir Starmer's two top aides knew Lord Mandelson failed security vetting weeks ago as pressure mounts to resign

Two of Sir Keir Starmer's senior civil servants knew Lord Peter Mandelson had failed the UK Security Vetting (UKSV) process weeks ago as Downing Street faces "judgement day" next week.

After Sir Olly Robbins was forced out of his job as Permanent Secretary of the Foreign Office on Thursday, it has emerged he was not the only civil servant to know the former ambassador to the US had not cleared the vetting process.

Sir Keir said he was "furious" to not be told Lord Mandelson had failed to pass his security vetting, with the Government saying he was not aware until earlier this week.

But it has emerged Dame Antonia Romeo, the head of the Civil Service, and Catherine Little, Cabinet Office Permanent Secretary, have both been aware since March, the Guardian reported.

Dame Antonia was told about Lord Mandelson's failure to clear security clearance by Ms Little.

A government source said Ms Little, the top civil servant in the Cabinet Office - which runs UKSV - was not sitting on the information but attempting to establish the risk of sharing highly sensitive information.

Government sources said Ms Little had been in favour of disclosing the outcome of the UKSV process to the public, but officials in the Cabinet Office were divided on how to proceed.

Some argued it would be "unprecedented" to disclose the file, as officials also asked the Foreign Office why it had granted him developed vetting clearance against advice.

The Cabinet Office also involved lawyers to determine if releasing information could prejudice the Metropolitan Police's criminal investigation into Lord Mandelson.

Up to a dozen officials and lawyers were aware of the vetting failure in the process, it has been suggested.

Sir Keir has maintained he did not know of the former US ambassador's vetting failure until earlier this week.

The back and forth on how to proceed will not ease concerns the Government is being run by mandarins rather than ministers.

A readout of a Tuesday meeting, published by Downing Street on Friday night, seemed to support the reporting from The Guardian.

LORD MANDELSON SCANDAL - LATEST:

• Keir Starmer fumes over 'unforgivable' Lord Mandelson chaos as he flees to France for key summit
• Lord Mandelson scandal proves broken state needs 'real outsiders', says Whitehall whistleblower
• Keir Starmer accused of avoiding scrutiny with plot to CANCEL Prime Minister's Questions

It said: "There is some discretion for departments to proceed with clearance and the FCDO had exercised it in this case, granting Mandelson vetting clearance.

"Cat [Ms Little] had not seen the audit trail for this decision so we did not yet know on what basis the decision had been taken, contrary to the recommendation.

"The PM was not aware of any of this before the meeting, including that it was even possible to grant clearance against the advice of UKSV."

Ciaran Martin, a former chief executive of the National Cyber Security Centre and friend of Sir Olly said he could not "comprehend the basis of the decision" to fire the former top Foreign Office official.

Dame Antonia - the first woman to hold the role of head of the Civil Service - was appointed on 19 February, and would have only been in the role for a few weeks.

She is said to have been supportive of the process to determine how move forward conducted by Ms Little.

The Prime Minister is now expected to face a "judgement day" next week, with Sir Olly expected to appear before the Foreign Affairs Committee as early as next Tuesday.

One senior MP told The Guardian they would be "amazed" if Sir Olly "didn't keep receipts".

The Cabinet Office denied Ms Little had sat on details, with a Government source saying "Cat has been the one doggedly fighting Olly Robbins to get the documents out of his clutches and into the public domain.

"This is a laughable attempt to shift blame from the actual person who kept the PM in the dark."

There are cross-party calls for Sir Keir to resign from all leaders of the major opposition parties.

A Cabinet Office spokesman said: "As part of the Government's commitment to comply fully with the Humble Address, the Permanent Secretary at the Cabinet Office requested the vetting summary document.

"Once she received this document, the Cabinet Office immediately undertook a series of expedited checks in order to be in a sound position to share the document, or the fact of it.

"As soon as these checks were conducted, the Prime Minister was informed."