British Prime Minister Boris Johnson’s right-hand man has left Downing Street after a power struggle that has rocked the administration.

Dominic Cummings exited No.10 carrying a large box on Friday evening following a bitter dispute that also led to the resignation of Cummings’ fellow Vote Leave veteran Lee Cain as communications chief this week.

Edward Lister was announced as the interim chief of staff pending a permanent appointment.

The dramatic events have come with Brexit headed to a crucial phase next week as London seeks a trade deal with Brussels before the end of the transition period on December 31.

The Sun reported there was a “shouty” confrontation between Johnson and Cummings over the ousting of Cain and a “livid” prime minister wanted both out “sooner rather than later”.

The BBC reported Cummings’ departure had been brought forward given the “upset in the team” and the PM wanted to “clear the air and move on”.

Some media reports have said Cummings has quit his post with immediate effect. PA understands he and Cain will still be employed until the middle of next month, with other reports suggesting Cummings will work from home.

Despite the controversy surrounding the two departures, Cummings has said his “position hasn’t changed since my January blog”, in which he said he hoped to be “largely redundant” by 2021.

Conservative backbenchers have urged No.10 to use the exit of the aide as an opportunity to restore several important values in the relationship between No.10 and Tory MPs.

Senior Tory MP Bernard Jenkin said it was time to restore “respect, integrity and trust” to the relationship, elements which had been “lacking in recent months”.

The Daily Telegraph said tensions within No.10 were running high, with Cummings accused of briefing against the prime minister.

It was also suggested Johnson was angered by claims a faction headed by Cummings and Cain had been “briefing against him” and his fiancee Carrie Symonds.

-AAP