Southport
Kemi Badenoch and Robert Jenrick used the updates about suspect Axel Rudakubana to hit out at Downing Street.
It's part of the Reform UK leader's wider claim there is "two-tier policing" in the UK.
The Grammy winner previously said she was "completely in shock" about the fatal stabbing.
Johnson was the London mayor in 2011 when violence broke out in the capital.
The PM suggested the government may revisit its policies for online platforms after the recent riots.
The new PM is being tested by his first major crisis barely a month after Labour's historic election victory.
"I'm sick of people making a small minority in society the scapegoat for all the problems," she said.
Nick Thomas-Symonds torched the Conservatives' legacy.
The X boss pulled PM Keir Starmer into a war of words over the wave of far-right violence.
Keir Starmer held a third emergency COBRA meeting on Thursday evening.