Former home secretary Jack Straw waded into the so-called plebgate row as he demanded the Government seeks answers to why the police investigation has suffered from "inordinate and unjustified delays".
The Labour MP has written to Home Secretary Theresa May exactly one year after Andrew Mitchell, whom he describes as a "personal friend", found himself at the centre of allegations that ultimately led to his resignation as Tory chief whip.
Mr Straw's letter comes shortly after ex-director of public prosecutions Lord Macdonald said it is "outrageous" that Scotland Yard is yet to publish a conclusion about the 45-second incident outside Downing Street on September 19 last year.
He said: "I may be on a different political side from Mr Mitchell, but I am also a friend of his, and have a high respect for his abilities and integrity too. No one, whatever their position, should have to suffer the toll which all this has taken on Andrew and his family. It's high time these delays were brought to an end."
Mr Straw said while it is not the role of the Home Secretary to "seek to influence the outcome of any investigation", her statutory responsibilities for the overall supervision of the police mean it is reasonable for the minister to seek answers to a number of questions.
He urges Mrs May to find out what is causing the delays in the investigation, when it is expected to finish and how the initial police account was provided to The Sun newspaper.
Mr Straw writes in the letter: "As a colleague of Andrew's you will be aware of the toll which all this has taken on him and his family. As a friend of his, I certainly am, and think that some conclusions should be reached, so that he and his family can get on with their lives, and he can resume his career."
The "plebgate" row ignited when Mr Mitchell was accused of launching a foul-mouthed rant at officers guarding Downing Street as he asked to cycle through the main gates. Pressure intensified after the Daily Telegraph published a police log of the incident, which claimed he called officers ''plebs'' and swore at them repeatedly for making him walk through a side gate. He insisted he did not use the words attributed to him, and later said he was the victim of a deliberate attempt to ''toxify'' the Tories and ruin his career.
A Channel 4 investigation cast doubt on the officers' account when it revealed CCTV footage which showed there was not a large group of tourists outside the main gate at the time as had originally been claimed. An email from a civilian witness backing up the police account of events has also been called into question.
The Metropolitan Police have said the inquiry is complicated and will "take as long as is necessary", while the Independent Police Complaints Commission, which is supervising two investigations into the incident, has said "all that can be done to conclude the investigation is being done".