Sandra Laville, crime correspondent for the Guardian newspaper, said an "over-reaction" to the crisis had led to a clampdown on all but the most senior officers talking to journalists.
In a statement to the Inquiry, Miss Laville said that as a result: "Any officer meeting a journalist to make them aware of a pressing issue within the police…to highlight racism, corruption or incompetence, is at risk of a criminal investigation and a disciplinary hearing."
The Metropolitan Police has come in for repeated criticism over its close relationship with News International, and in January a report by Elizabeth Filkin, the former parliamentary commissioner for standards, suggested that reporters and police officers should not met over alcoholic drinks.
The report also called for "more open and impartial" provision of information to the public, but Miss Laville said its recommendations were likely to have "the opposite effect".
She said one recommendation in the report, that all leaks to journalists should automatically be the subject of a criminal investigation, "could be seen as criminalising informal contacts between the police and journalists" which are vital for holding the police to account.
"It is not enough that the flow of information from a police force is controlled by senior officers and their management board, who are driven by the need to protect the corporate image of the police force," she added.
Miss Laville cited the case of Kirk Reid, a serial rapist who was finally jailed for life in 2009 following years of incompetence by the Met, which had failed to bring him to justice earlier despite dozens of women being attacked by him for almost a decade.
The Met had chosen not to highlight the case - which eventually led to a damning report by the Independent Police Complaints Commission - and it was only because an individual police officer tipped off the media that it came to be reported.
Miss Laville said that in the current climate, the officer who tipped her off about the Reid case would be liable to criminal prosecution even though he was acting "in the public interest" by ensuring the Met's failures were brought to light.
Junior officers "are already refusing to talk to journalists", she said: "Because there is now a growing culture of fear within Scotland Yard that if they do so they will be subjected to a criminal investigation, and/or sacked."
She pointed out that it was senior officers and managers, not middle and lower-ranking officers, who were criticised for their "cosy" relationships with newspaper executives, yet the Met's response has been to give the senior officers and managers even more power.
She cited the example of Sir Robert Mark, who faced a corruption scandal in the 1970s and responded by telling rank and file officers to go out and speak freely, with his full support, to ensure corruption would be quickly exposed in future, and suggested he had struck "the right balance".