Boris Johnson went 'f***ing tonto' and 'threatened to demote Rishi Sunak to Health Secretary' after the Chancellor called for easing of travel restrictions, reports suggested.  

The Prime Minister made his remarks to MP allies after a note written by the Chancellor a month ago found its way into the public domain last weekend - shortly before the infamous 'traffic light' rules were reviewed on Thursday.

In his letter, Mr Sunak said that the UK was 'out of step' with the rest of the world.

Mr Johnson told his allies that by writing the letter, which was copied to Grant Shapps's Transport Department, it was 'bound' to be leaked - and fumed that he could move Mr Sunak to Health, where former Chancellor Sajid Javid became the Secretary of State six weeks ago. 

Mr Johnson was said to have been 'apoplectic', 'raging' or 'f***ing tonto' when he met senior Downing Street aides on Monday, reports.

He suggested sacking Rishi Sunak following the chancellor's remarks calling for an easing of travel restrictions due to the threat they pose to the economy.

The first time the PM heard about the letter was when details of it appeared in news outlets, meaning officials had not flagged it for his attention or put it in his ministerial red box, it is believed.  

A senior source said the PM reportedly demanded to know where Mr Sunak was, and then in front of more than 12 witnesses said: 'I've been thinking about it.

Maybe it's time we looked at Rishi as the next secretary of state for health. He could potentially do a very good job there.' 

But it could be the case that Mr Johnson will not carry out his threat, as it has been reported that the Prime Minister has a reputation for off-the-cuff remarks made 'half in jest'. 

He then suggested Mr Sunak 'could be demoted in the next reshuffle', the source said.