- Video report by ITV News Correspondent Angus Walker
Theresa May has spoken for the first time about sacking Gavin Williamson and said she made the ''right decision''.
Speaking to ITV Wales, the Prime Minister said she had no regrets about firing Mr Williamson from the role of Defence Secretary earlier this week.
Mrs May was asked whether she stood by her choice and replied: ''I did take a difficult decision.
"This was not about what was leaked it was about where it was leaked from. It was the importance of the question of trust around that National Security Council table.''
Asked whether she was convinced Mr Williamson was the source of the leak relating to the possible awarding of a contract to build the UK's 5G network to Huawei, she said: ''I took the decision that I did and that was the right decision.''
Mrs May has faced a growing backlash over her treatment of Mr Williamson, who insists he did not leak highly sensitive information about the government's 5G Huawei deal discussed during a National Security Council meeting.
The ruthless manner in which she dispatched Mr Williamson, who until recently was her closest ally has divided opinion among MPs.
Some have called for Mr Williamson to be prosecuted after it was suggested he had breached the Official Secrets Act.
Others believe he should be allowed a chance to defend himself in an official investigation.
It has also been reported he is thinking of delivering a speech like Geoffrey Howe’s resignation speech which sparked Margaret Thatcher’s downfall.
The former Chancellor's speech in 1990 revealed he and Lady Thatcher had disagreed over the EU.
His words encouraged Michael Heseltine to challenge Mrs Thatcher's leadership and within weeks she left Number 10.
The government does not think it necessary to refer the National Security Council leak to the police, the PM's de facto deputy said earlier this week.
Responding to calls from MPs for a police inquiry, David Lidington said the PM considered the matter "closed".
He said Mr Williamson had not been accused of a criminal offence, but had lost the PM's confidence.
It is understood Cabinet Secretary Sir Mark Sedwill found the information leaked was not of a classification level which would make its disclosure a criminal act.