City MP Keith Vaz has said public confidence in the police has been shaken due to a "dangerous cocktail" including the "plebgate'' affair and the results of the Hillsborough Inquiry.
The Leicester East MP is chairman of the Home Affairs Select Committee which will begin an inquiry into police accountability, integrity and internal corruption next month.
He has called on Prime Minister David Cameron to host annual summits with senior officers and for there to be a "a new Magna Carta'' for policing.
Writing in the Sunday Express about the alleged altercation between former chief whip Andrew Mitchell and police officers at the gates of Downing Street, dubbed "plebgate'', Mr Vaz said: "What appears to have happened to Andrew Mitchell could well have been a Christmas special script. The chief whip had to resign following a 60-second 'incident' in, of all places, Downing Street.
"Take a police officer apparently masquerading as a member of the public, a confidential logbook finding its way into the public domain, add the results of the Hillsborough Inquiry, which have resulted in thousands of serving and former police officers being investigated, and the fact that 26 out of the 43 police forces do not have a permanent chief constable, and you have a dangerous cocktail.'
"This is a defining moment for policing. Cool heads, clear thoughts and strong leadership are required."
Mr Vaz also criticised Home Secretary Theresa May for trying to enforce radical changes on the police force without having a proper dialogue with officers.
He acknowledged existing police structures needed to be reformed, but said Mrs May's changes were "too rapid and too far-reaching''.
In the article, Mr Vaz rounded on the Government for altering police officers' pay and conditions while trying to implement reforms.
"The Government was wrong to change police pension arrangements retrospectively. It was unfair and forced out a number of experienced officers,'' he said.
Mr Vaz's committee will next month launch an inquiry into issues of police training, accountability and integrity and into the effectiveness of the processes for dealing with internal corruption and malpractice in the force.
He has also called for there to be a Royal Commission for the police service to explain what it is doing and for the public to say what they want it to do.
He wrote: "We need a Royal Commission that sets out a new Magna Carta for policing in this century."
However, the Home Office has said surveys regularly showed public confidence in the police remained high. The 2011/12 Crime Survey for England and Wales showed that just under two-thirds of adults thought the police in their area were doing a good or excellent job.
A Home Office spokesman said: "Police reform is working and crime is falling. The police budget is £14bn a year and it's only right that they should make a contribution to reducing the budget deficit.
"Chief constables are rising to the challenge of making efficiency savings and providing greater value for money."
