Five senior people have resigned from Boris Johnson’s office at 10 Downing Street, within a 24-hour period but the one departure that has taken everyone by surprise is that of Munira Mirza, a 43-year-old Pakistani origin woman with whom he has worked closely for the past 14 years.

Hardly anything was known about her till a couple of years ago when Boris named Munira as one of five women who had influenced and inspired him the most. He described her as “capable of being hip, cool, groovy and generally on trend”. It is fair to say that in his own way, Boris is quite progressive in his dealings with non-white people.

It is obvious that Munira’s resignation has wounded him deeply, both personally and politically. What has caused a falling out between Boris and Munira is not “Partygate” but an exchange between the Prime Minister and the Labour leader, Keir Starmer, in the Commons on Monday.

Boris referred to the late TV presenter, Jimmy Savile, who was knighted by Margaret Thatcher for his charitable work but it was later revealed he had “sexually abused 72 people and had raped eight, including an eight-year-old”, according to an official report.

Boris responded to Starmer’s barbs over “Partygate” by recalling Starmer’s period as director of public prosecutions from 2008 to 2013.

The Prime Minister retorted by accusing the Labour leader of trying to “prejudge a police inquiry”, adding that as director of public prosecutions, Starmer had “spent most of his time prosecuting journalists and failing to prosecute Jimmy Savile”.

Many Tories thought this was an unseemly slur and urged Boris to apologise.

On Thursday, during a visit to Blackpool, Boris was challenged to withdraw the remark, and said: “I want to be very clear about this because a lot of people have got very hot under the collar, and I understand why. Let’s be absolutely clear, I’m talking not about the leader of the Opposition’s personal record when he was director of public prosecutions and I totally understand that he had nothing to do personally with those decisions. I was making a point about his responsibility for the organisation as a whole. I really do want to clarify that because it is important.” This was not enough for Munira, whose letter of resignation found its way into The Spectator. She is married to Dougie Smith, who works for Boris but has not resigned. The couple have a child.

There are a great many personal relationships linking politics and journalism.

Munira told Boris in her letter: “I believe it was wrong for you to imply this week that Keir Starmer was personally responsible for allowing Jimmy Savile to escape justice.

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.

“You are a better man than many of your detractors will ever understand which is why it is so desperately sad that you let yourself down by making a scurrilous accusation against the Leader of the Opposition.”

“I appreciate that our political culture is not forgiving when people say sorry, but regardless, it is the right thing to do. It is not too late for you but, I’m sorry to say, it is too late for me.”The BBC is now saying that differences have opened up between the prime minister and the chancellor, Rishi Sunak.

When asked about Boris’s remark linking Starmer with Savile, Sunak told a Downing Street conference on Thursday: “Being honest I wouldn’t have said it and I’m glad that the prime minister clarified what he meant.”

The others who have resigned from 10, Downing Street, which is both an office where over 300 people work as well as the prime ministers home, include: Martin Reynold, his principal private secretary (he invited about 100 people to “bring your own booze” party); Dan Rosenfield, chief of staff; Jack Doyle, who left the Daily Mail to become director of communications; and Elena Narozanski, an education policy specialist.