The former head of MI6 directed a criticism towards the two potential Prime Ministers on Saturday during an interview with the BBC, saying that the UK is going through a “political nervous breakdown”.
The ex-Mi6 chief said Britain could soon have a Prime Minister who does “not have the standing that we have become used to in our top leadership”.
Sir John’s comments come as Britain is geared to see the appointment of a new prime minister by the Conservative Party on the 22nd of the July.
Sir John also expressed concerns regarding Brexit:
"I think there is a lot of anxiety as we leave the European Union, we take a huge risk to our international standing, to the strength of the British economy."
He called former-Prime Minister David Cameron “unwise” for calling the 2016 EU referendum, saying it had left the country “badly divided” and diminished the UK’s standing on the world stage.
Former Secretary of State for Work and Pensions and Boris Johnson supporter, Iain Duncan Smith, rebuked Sawer’s comments, saying “democracy may well frighten him” and instructing him not to “lecture” the party.
His criticisms did not end at the Tory leaders however, they were also directed at the opposition leader.
“We have potential prime ministers being elected by the Conservative Party now, [and] in the shape of the leader of the opposition, who do not have the standing that we have become used to in our top leadership.
Sir John’s comments regarding Mr Corbyn echoed recent statements from officials who accused the leader of being too “frail” to lead the country.
It would also not be the first incident where senior civil servants expressed disdain towards the idea of a Labour government.
In 2015 an unnamed general said the armed forces could potentially sabotage a Corbyn government’s efforts to scrap Trident, end NATO membership, or try “to emasculate and shrink the size of the armed forces.”
Mr Corbyn's office told the BBC it would not respond to Sir John's comments