"[The UK prime minister] has thanked [Rosenfield and Reynolds] for their significant contribution to government and No 10, including work on the pandemic response and economic recovery," the spokesperson noted.
"They will continue in their roles while successors are appointed, and recruitment for both posts is underway."
Doyle reportedly told staff that recently working at 10 Downing street had "taken a terrible toll on my family life."
A Number 10 spokesperson said of Doyle's resignation: "Jack Doyle has left government. He has made a huge contribution and the prime minister is immensely grateful for the work he has done."
On Monday, Johnson accused Starmer, while the former was director of public prosecutions (DPP), of spending "most of his time prosecuting journalists and failing to prosecute Jimmy Savile."
Mirza wrote in her resignation 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 desperately sad that you let yourself down by making a scurrilous accusation against the Leader of the Opposition," she observed.
"Even now, I hope you find it in yourself to apologise for a grave error of judgement made under huge pressure. 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."