The Government has ruled out legal changes to curb police spying on journalists before the general election on 7 May 2015.
And it has suggested that the police use of the Regulation of Investigatory Powers act to view the phone records of journalists at The Sun was warranted because the investigation involved "allegations of a police conspiracy against the Government".
The Crown Prosecution Service declined to prosecute the three officers accused of leaking information to The Sun because it said a jury would decide they acted in the public interest by revealing information about the Plebgate incident of September 2012.
Last week Lord Strasburger tabled an amendment to the Serious Crime Bill which sought to ensure that police officers obtain the approval of a judge before viewing the phone records of journalists. Despite cross-party support, the Government declined to back it.
Home Office minister Lord Bates explained why the Government refused to back the measures in a letter this week to Lib Dem peer Lord Strasburger who tabled the amendment.
He said: "RIPA is clear that acquisition of communications data must be necessary for one of the specific and legitimate purposes set out in the Act, including for example the prevention and detection of crime and the safeguarding of national security, and proportionate to what is sought to be achieved.
"It cannot lawfully be used simply to identify journalists' sources."
He added: "In that context, you may be aware that in a letter to the Times on 17 October the Director of Public Prosecutions wrote: 'The two cases [Chris Huhne and Operation Alice] involved a part-time judge deliberately perverting the course of justice for which she was jailed, and allegations of a police conspiracy against the Government; this was not about either a confidential tip-off over speeding fines or the sources of an embarrassing leak.'"
In the Chris Huhne case, Kent Police secretly gained access to the phone records of two journalists working for the Mail on Sunday who were not under suspicion of breaking the law.
Lord Bates omitted to mention the Suffolk Police case of 2006. The force has now admitted it used RIPA to obtain the phone records of a journalist purely in order to find the source of a leak. The officer concerned was not formerly disciplined.
Press Gazette has discovered that UK forces conducted more than 300 leak inquiries in a five-year period to 2011. The forces concerned have so far refused to reveal whether RIPA was used against journalists in these cases.
Lord Bates said that a review of the operation of regulation and investigatory powers by David Anderson will report on 1 May, six days before the general election.
He said the review welcomes submissions from any party and Press Gazette will be submitting the Save Our Sources campaign and petition (which as 1,250 signatures) to him.
Lord Bates added: "The upcoming public consultation on the revised RIPA acquisition code of practice provides an opportunity for anyone to provide views on, amongst other things, additional protections for those sensitive professions, including journalists and those in the legal profession.
"The Interception of Communications Commissioner has already said he will be responding to that consultation. Ultimately the revised code must be debated and approved by both Houses of Parliament.
"I entirely share your concern that the powers available to public authorities in this area must not be abused; to do so undermines those powers and therefore undermines the legitimate purpose behind them. However, I hope you can agree that it would be premature to take legislative action in advance of the findings of the significant reviews that are currently underway."
The Home Office said that revised RIPA code of practice will be published in the "autumn" and then go out to public consultation before being put before Parliament.