Cabinet Secretary Sir Jeremy Heywood was sharply criticised by The Commons Public Administration Committee for his investigation into former chief whip Andrew Mitchell's "plebgate" row with Downing Street police officers.
"The Prime Minister remains of the view that it was the right review at the right time," is the answer Number 10 is giving to the Public Administration Committee's scathing report on the 'Plebgate' investigation.
The PM continues to take a strong view that his request to the Cabinet Secretary to look into the emails and see whether they changed his initial judgment was the right request at the time. There is nothing in the report which alters this view.
The Cabinet Secretary's advice was very clear the emails were unreliable and should not be taken into account. The PM concluded Andrew Mitchell should stay in post. The Cabinet Secretary's review did not in any way lead to Andrew Mitchell's departure.
It would also have been entirely inappropriate for the Cabinet Secretary to conduct a freelance private investigation into the veracity of the police.
The Commons Public Administration Committee chairman Bernard Jenkin, said: "This underlines the all-too-obvious truth that investigations into ministerial misconduct are not an appropriate role for the Cabinet Secretary to undertake.
"Given time, attention and with his relevant experience, Sir Alex Allan (a former chairman of the Joint Intelligence Committee) might well have uncovered the truth."
Regardless of what the Prime Minister had or had not asked him to do, on establishing that there were unanswered questions about the incident, Sir Jeremy should have advised the Prime Minister that these questions required further investigation and therefore a wider inquiry.
The events leading to the resignation of the Government Chief Whip again demonstrate that the Cabinet Secretary is not the appropriate person to investigate allegations of ministerial misconduct.
His role is limited; there is already intense pressure on his time and attention; and his role as impartial investigator may conflict with his primary role, which is to support the daily work of the Prime Minister and the Government as a whole.
The Commons Public Administration Committee listed a number of errors in Cabinet Secretary Sir Jeremy Heywood's inquiry into former chief whip Andrew Mitchell's "plebgate" row.
The committee said it was "surprising" that Sir Jeremy had not been aware of a note of a conversation that the No 10 head of security and the Prime Minister's principal private secretary had with the officer concerned shortly after the incident.
They said it was "equally surprising" that he did not establish whether a reported leak of the police log was actually true.
Sir Jeremy should have advised David Cameron to refer the matter to the relevant police authorities so they could resolve any "discrepancies and inconsistencies", they added.
Cabinet Secretary Sir Jeremy Heywood was criticised by MPs for his investigation into former chief whip Andrew Mitchell's "plebgate" row with police officers at Downing Street.
Sir Jeremy was not the "appropriate figure" to carry out such an inquiry and suggested that his role as an "impartial investigator" was compromised, The Commons Public Administration Committee said.
Mr Mitchell was forced to resign following claims that he swore at the officers and called them "plebs" after they refused to allow him to cycle through the main gates at Downing Street.
However, evidence has emerged casting doubt on the police account of events - which Mr Mitchell has always strongly disputed, insisting he did not use the word "pleb" and only swore once under his breath.