More than 100 senior editors representing every UK national newspaper, the regional press and broadcasters have signed a letter urging David Cameron to intervene to help protect journalists’ phones and communications records from being secretly snooped on by police.

The letter calls on the prime minister to consider changes to a draft code of practice put forward by the home secretary, Theresa May, to meet concerns over the police use of surveillance powers linked to the Regulation of Investigatory Powers Act 2000 (Ripa). The letter, signed by senior industry figures including Guardian editor-in-chief Alan Rusbridger as part of a campaign organised by the Society of Editors and industry news website Press Gazette, states that the new code “appears to do very little which would stop a repeat of such abuse of Ripa”.

May had offered to provide guidance over existing police powers after it emerged the Metropolitan police secretly accessed the phone records of Sun journalist Tom Newton Dunn to find the people who had leaked him information in the Plebgate affair. Critics of May’s safeguards fear that the police will still have sweeping powers allowing them to authorise themselves to access the phone and email records of professionals such as journalists, lawyers, doctors, MPs and priests who handle privileged, confidential information.

The letter adds: “The code needs to balance the seriousness of the alleged crime against the public interest in protecting the confidentiality of all journalistic sources and potential whistleblowers.

“The guidance needs to make it clear that a public official communicating information to a journalist without official approval (ie. a leak) cannot be sufficient justification for a Ripa telecoms request.”

Cameron has called for an extension of the laws that give snooping powers to security services with a plan to ban encrypted messages in the wake of the Charlie Hebdo Paris attacks.