Scotland Yard is investigating how the Sun and the Daily Telegraph got hold of information about “Plebgate” and whether there was a leak from police.
Andrew Mitchell’s claims that police lied in the log of the event and a police officer's claim to have witnessed the altercation are also being looked into by Scotland Yard.
Three officers have so far been arrested as part of the investigation.
Papers related to the case were passed to prosecutors on Thursday.
A number of newspapers have reported that the file does not contain evidence that officers lied about an altercation with Mitchell in Downing Street.
Andrew Mitchell, who has made a former complaint against Scotland Yard over the alleged leaking of its “Plebgate” report, has strongly criticised the Met’s handling of the situation.
In a letter to IPCC deputy chairman Deborah Glass, he wrote:
We are deeply dismayed that the Metropolitan Police appear to have leaked part of their Report prepared for the Crown Prosecution Service (CPS) to certain members of the Press and spun it to the advantage of the Police officers involved.
– Andrew Mitchell
This was an Enquiry into a dishonest and illicit attempt to blacken my name and destroy my career. It would appear that this police enquiry continues precisely that process.
Andrew Mitchell, the former Cabinet Minister, has made a formal complaint against Scotland Yard over the alleged leaking of its report into the “Plebgate” affair.
Mitchell made the move after Friday’s newspapers suggested a police file handed to the Crown Prosecution Service contained no proof that police officers lied about the incident.
The Tory MP has written to the Independent Police Complaints Commission (IPCC) accusing the Metropolitan Police of a continued campaign to "destroy" his career.
Andrew Mitchell's lawyer has confirmed that the MP has taken legal action against the Sun and indicated that "other potential actions" were being considered.
Graham Atkins said: "I can confirm that I recently issued proceedings for libel against the owners of The Sun on behalf of Andrew Mitchell MP.
"There are a number of other potential actions being considered but I do not intend commenting any further at this stage."
The Conservative MP is suing The Sun over its reporting of his infamous row with officers in Downing Street as a file investigating police involvement in the incident is passed to prosecutors.
ITV News' Political Correspondent Alex Forrest reports:
The newspaper said it is understood there is nothing in the file to support a claim that Met police officers were involved in an conspiracy to frame the former chief whip.
Andrew Mitchell's lawyers sent The Sun a "letter before action" last month, putting it on notice that the Conservative MP intended to sue.
At the time, his lawyer Graham Atkins told The Guardian: "We are seeking damages, an apology, an undertaking that the words complained of are not repeated, and costs."
The newspaper was the first to break the story of Mr Mitchell's row with the officers at Downing Street, which became known as the "Plebgate" scandal.
The Sun's political editor Tom Newton Dunn has confirmed the newspaper will defend itself against a libel writ from Andrew Mitchell.
Statement issued by The Sun tonight re #plebgate: A Sun spokesman: "We stand by our story and will defend this claim vigorously".