Theresa May could afford to sack Gavin Williamson over the Huawei leak as he was “not the Lionel Messi of the cabinet”, a former top civil servant has said. 

Lord Gus O’Donnell made the unflattering comments about the former defence secretary after the PM brutally fired him on Wednesday night. 

It followed an internal investigation into how discussions about the role the Chinese telecoms could have in building Britain’s new 5G mobile network at the National Security Council were leaked to the Daily Telegraph. 

After it emerged that Williamson had an 11-minute conversation with the paper’s journalist Steven Swinford, May said there was “no other credible version of events” than the ex-defence secretary being the culprit. 

But her one-time chief whip has vehemently denied the allegation and, in an apparent swipe at cabinet secretary Sir Mark Sedwill, who led the probe, said a full police investigation would exonerate him. 

O’Donnell defended Sedwill, however, and said the decision to move against Williamson was May’s alone and that the PM had calculated she could “do without” him. 

Speaking on BBC’s Radio 4 Today programme, he said: “The cabinet secretary is giving advice to [May]. The cabinet secretary is saying this is a matter for the violation of the ministerial code, it is not a breach of the Official Secrets Act that is putting lives at risk. 

“That is why it is a matter for the prime minister to decide does she want this person in her team when faced with this evidence and she has basically decided he is not the Lionel Messi of the cabinet and she can do without him.

“His job [Mark Sedwill] is to defend the principle of cabinet government, to look after the security of the National Security Council (NSC) and to advise the prime minister. She decides on what action to take and it is her that decided on the basis of this evidence that she wanted to say farewell.”

It comes as a government minister will be expected to appear in the Commons on Thursday morning to respond to an urgent question from Labour’s deputy leader Tom Watson over the sacking. 

Asked whether there should be a police inquiry into the leak and Williamson’s conduct, O’Donnell said: “Well it’s perfectly legitimate for anyone to ask the police to investigate something – it’s up to the police then to discuss it.

“But they will face exactly the same issues we’ve been talking about, will they get a journalist on the record to disclose what has been said?”

Ex-Army chief General Lord Dannatt, meanwhile, defended Gavin Williamson’s performance as defence secretary.

He told the Today programme: “This is a personal tragedy for Gavin Williamson; it’s also something of a tragedy, certainly very upsetting, for defence at the present moment.

“It’s a very difficult brief, people take quite some time to learn it, and he has got to grips with it pretty well over the last 18 months.

“He got £1.8 billion extra in the Budget last year and was continuing to argue the case for more resources in the Spending Review and he was fighting his corner.

“Yes, he made some mistakes, he made some gaffes, and said some things that he probably regretted, but on the whole he was doing a good job.”