Legislation introduced to fight serious crime should never be used by police to spy on journalists and reveal the identity of their sources, Culture Secretary Sajid Javid has said.
His comments came as he promised new protections for journalists and the free press in the British Bill of Rights which David Cameron has said he will introduce if the Conservatives win next year's general election.
Home Secretary Theresa May last month announced a review of the Regulation of Investigatory Powers Act (Ripa), after it was revealed that police forces had used it to snoop on journalists and access their phone records to identify sources.
In a speech to the Society of Editors annual conference in Southampton, Mr Javid said that the right for reporters to keep sources anonymous was "sacrosanct" and that Ripa had been used "in a manner for which it was never intended".
"The right to keep sources anonymous is the bedrock of investigative journalism," the Culture Secretary told his audience of newspaper editors.
"Without it, you cannot do your jobs. Without it, the corrupt and the crooked sleep easier in their beds.
"It's a sacrosanct principle and one that the authorities need a damn good reason to interfere with.
"Ripa was passed to help with the fight against serious criminal wrongdoing, not to impede fair and legitimate journalism, no matter how awkward that journalism may be for police officers and local councils.
"The legislation should never be used to spy on reporters and whistleblowers who are going about their lawful, vital business.
"I know Theresa May is doing what she can to stop this happening. As the Secretary of State responsible for the media, I'll be making sure the Home Office knows just how important this issue is for the industry. And I'll be watching closely to ensure the Act is not misused in future."
Mr Javid did not give details of the new protections which the press might gain from the mooted Bill of Rights, which would replace the Human Rights Act and give MPs the power to overrule the European Court of Human Rights. Sources said further details were expected around the turn of the year.
The Culture Secretary said the European court had introduced "censorship through the back door" by ordering internet search engines such as Google to offer a "right to be forgotten" to individuals who want links to information about them to be removed.
And he said that Article 8 of the European Convention on Human Rights was being used as "an excuse for well-paid lawyers to hide the shady pasts of wealthy businessmen and the sexual indiscretions of sporting celebrities".
Mr Javid said: "If we receive a majority at the next election, a Conservative government will scrap Labour's Human Rights Act and deliver a new British Bill of Rights and Responsibilities. Passed in our Parliament and rooted in our values, it will restore British judges as the ultimate arbiters of British justice.
"And today I'm delighted to announce that I have agreed with the Justice Secretary that the British Bill of Rights will include specific protection for journalists and a free press.
"The Human Rights Act and the European courts have not done enough to protect journalists who play such a unique role in our society. Our British Bill of Rights will change that."
Mr Javid hailed the freedom of the press as "one of the fundamental liberties on which modern Britain was built", and said that newspaper journalists were "the right people - the only people - to take the lead on developing and enforcing a new set of press standards".
In the wake of the Leveson Inquiry into press standards, the Government last year passed a royal charter intended to underpin a new press watchdog. However, the process has not won industry backing and a number of newspapers have established an Independent Press Standards Organisation (Ipso) which does not have the backing of the charter.
Since replacing Maria Miller as Culture Secretary earlier this year, Mr Javid has made clear he believes the Government has no further role to play in the system of press regulation.
He told the Society of Editors: "Unethical or inaccurate reporting should be policed not by the state but by an industry-led regulatory system.
"A system that ensures standards are upheld, complaints are heard and there is proper redress for those who have been wronged."
And he added: "This Government has absolutely no intention of imposing any form of state-controlled regulation of the press.
"No government ever should. The process must be industry-led, with no opportunity for politicians, present or future, to interfere with legitimate journalistic practice."