Mr Johnson has also yet to outrun Neville Chamberlain.
06 June 2022
Boris Johnson faces a vote of confidence in his leadership just one day before he equals the number of days spent as prime minister by his Labour predecessor Gordon Brown.
Mr Johnson is currently on the 1,048th day of his premiership, just behind the 1,049 days clocked up by Mr Brown between June 2007 and May 2010.
He has already overtaken four prime ministers with the shortest time in office since 1900: Andrew Bonar Law (211 days in 1922-23), Alec Douglas-Home (364 days in 1963-64), Anthony Eden (644 days in 1955-57) and Henry Campbell-Bannerman (852 days in 1905-08).
Once he has passed Mr Brown, the next prime minister on the list is Neville Chamberlain, who was in office for 1,078 days from 1937 to 1940.
Mr Johnson would overtake Mr Chamberlain in just over a month, on July 7.
His immediate predecessor as prime minister, Theresa May, clocked up 1,106 days in the job between 2016 and 2019.
To overtake her, Mr Johnson needs to remain as PM until August 4 this year.