- Munira Mirza has been advising Boris Johnson for more than a decade.
- She quit over his decision to invoke a far-right conspiracy theory about opponent Keir Starmer.
- One MP said it was "very damaging for Boris".
One of Boris Johnson's closest advisers quit on Thursday, citing the prime minister's use of a far-right conspiracy theory against his political opponent.
Munira Mirza, who worked with Johnson for more than a decade including during his time as London mayor, claimed it was "wrong for you to imply this week that Keir Starmer was personally responsible for allowing Jimmy Savile to escape justice."
In a letter published in The Spectator, she added: "There was no fair or reasonable basis for that assertion. This was not the usual cut and thrust of politics; it was an inappropriate and partisan reference to a horrendous case of child sex abuse.
"You tried to clarify your position today but, despite my urging, you did not apologise for the misleading impression you gave."
Her departure has already caused shockwaves in Westminster.
One MP told Insider it was "very damaging for Boris."
A senior Conservative figure simply texted: "Fuck."
Dominic Cummings, Johnson's former right-hand man, said it showed "moral courage" and was "an unmistakable signal the bunker is collapsing & this PM is finished."
This is a breaking news story.
