Spy chiefs and military top brass feared they could not speak freely at a secret security committee after a leak blamed on Gavin Williamson, Theresa May has revealed.
Mrs May was Prime Minister when she sacked Mr Williamson as Defence Secretary after blaming him for an unprecedented leak from the National Security Council.
She pointed the finger after details about Chinese firm Huawei being allowed to build 5G technology in the UK appeared in the press in May 2019.
Mr Williamson has always denied being responsible.
Giving evidence to Parliament's National Security Strategy Committee, Mrs May revealed the bombshell leak “shocked” committee members.
She told MPs and peers: “Obviously an incident like that is a shock to the system when it happens.
“There was a slight sense initially of concern, particularly obviously from those who weren't the politicians sitting around the table, about the advice and evidence that they were giving into the council because it had always been the case that the assumption – and it had practically been the case since it was setup – that nothing leaked from the National Security Council.
“It's really important that nothing leaks from it because of the nature of the discussions we're having.
“You want the agencies, Ministry of Defence and others who are advising you to believe and feel confident that they have the freedom to give their best and genuine advice without feeling that they have to hold something back.”
The incident triggered a “a slight judder” before people could trust each other again and “speak as freely as they had done previously”, she added.
Mrs May also blasted Boris Johnson's choice of National Security Adviser, ex-Brexit negotiator Lord David Frost, who has since been replaced by the Ministry of Defence's top official, Sir Stephen Lovegrove.
“The National Security Adviser is the person the Prime Minister and the Government look to to give absolutely critical, independent, well-analysed views on the security situation,” Mrs May said.
“I think therefore it is important that individual has experience in the security field.”
Necessary qualities for the role included “to have been in that world, to understand it and to be able to slot in immediately in dealing with these issues – and that was my concern about the appointment of David Frost,” said the ex-PM.
She praised Sir Stephen as being “an excellent appointment” who “will do a very good job”.
She added: “He's steeped in it, he understands a key element of national security”.
