Jo Johnson, Boris Johnson’s brother, has resigned as a minister and will step down as an MP, saying he was “torn between family loyalty and the national interest”.
The shock announcement adds to the pressure on the prime minister, injecting a family feud into the political crisis in Westminster.
Jo Johnson been appointed a universities minister when his brother became PM last month.
He raised eyebrows by accepting the position in a government willing to accept a no-deal Brexit, given he had been a vocal supporter of holding a second referendum.
A No. 10 spokesman said Jo Johnson had been “a brilliant, talented minister and a fantastic MP”, and the prime minister “as both a politician and brother understands this will not have been an easy matter for Jo”.
Angela Rayner, Labour’s shadow education secretary, said: “Boris Johnson poses such a threat that even his own brother doesn’t trust him.”
It comes after MPs rejected Boris Johnson’s call for a snap general election. The PM demanded a poll after rebel bill designed to require the government to ask for an Article 50 extension was passed by the Commons.
Labour refused to agree to the PM’s bid for an October 15 election, amid fears it was a “trap” that would allow him to later move polling day until after a no-deal exit from the EU.
Downing Street said the PM will this afternoon “speak directly to the public, setting out the vital choice that faces our country”.
Boris Johnson has already triggered a backlash among his own MPs after he purged the parliamentary party of 21 backbenchers, including Philip Hammond, who voted in favour of an Article 50 extension.
In a 2013 interview with the The Australian newspaper, Boris Johnson said politics would never divide his family like it had Ed and David Miliband.
“Only a socialist could do that to his brother, only a socialist could regard familial ties as being so trivial as to shaft his own brother,” he said.
Earlier this week former justice minister Philip Lee, who backs a second referendum, defected from the Conservative Party to the Lib Dems.