Parliament voted for the cross-party Privileges Committee to examine the matter last year.
In a statement, released at the same time as the committee's update, the former prime minister argued there was "no evidence in the report that I knowingly or recklessly misled parliament, or that I failed to update parliament in a timely manner."
"When I told the House that the rules and the guidance had been followed, that was my honest belief."
Here are the five key findings from the committee's interim report:
* Mr Johnson failed to tell MPs about his own knowledge of gatherings he attended
* Mr Johnson said he had relied upon repeated assurances that the rules had not been broken. However, the committee says it had not received any evidence that assurances were provided in relation to certain events
* Mr Johnson failed to reveal his "personal knowledge" of gatherings when telling MPs a formal inquiry would be needed to get to the truth
The committee says: "There is evidence that those who were advising Mr Johnson about what to say to the press and in the House were themselves struggling to contend that some gatherings were within the rules."
It quotes a WhatsApp from Downing Street's director of communications from 25 January 2022 in relation to a gathering of 19 June 2020 which says: "Haven't heard any explanation of how it's in the rules."
In another WhatsApp the adviser says of the same event: "I'm struggling to come up with a way this one is in the rules in my head."
In response to a suggestion that they could describe the event as "reasonably necessary for work purposes", then director of communications Jack Doyle says: "Not sure that one works does it. Also blows another great gaping hole in the PM's account doesn't it?"
The committee has written to Mr Johnson to confirm a date for him to appear before them.
The MPs have given Mr Johnson a period of "not less than two weeks in which to assess the report and evidence before he gives oral evidence".
The committee says it will make a judgement on whether Mr Johnson misled MPs.
If the committee finds that Mr Johnson recklessly or intentionally misled MPs, it will consider what sanctions to recommend, which could include suspension or expulsion from the Commons.
MPs will then have the chance to accept or reject the recommendations.