Chris Huhne who was jailed for eight months in 2013 when he admitted perverting the course of justice over a speeding case in 2003

Police used anti-terrorism powers to secretly spy on The Mail on Sunday after shamed Cabinet Minister Chris Huhne falsely accused journalists of conspiring to bring him down.

Detectives sidestepped a judge’s agreement to protect the source for our stories exposing how Huhne illegally conspired to have his speeding points put on to his wife’s licence. Instead they used far-reaching powers under the controversial Regulation of Investigatory Powers Act (RIPA) – originally intended to safeguard national security – to hack MoS phone records and identify the source.

They trawled through thousands of confidential numbers called by journalists from a landline at the busy newsdesk going back an entire year, covering hundreds of stories unrelated to the Huhne case.

MPs last night warned that police use of RIPA to spy on journalists was a disproportionate use of power that would deter whistleblowers from approaching the media because of fears they could be unmasked by police.

Keith Vaz, chairman of the Commons Home Affairs Select Committee, said: ‘It is deeply disturbing that the police have hacked into offices of a major UK newspaper. They have struck a serious blow against press freedom.’

Now, for the first time, the full extraordinary story can be told of Huhne’s arrogant crusade to evade justice with lie after lie following the MoS’s revelation of his crime.

It strikes at the heart of one of the bulwarks of a free, independent, press: the right of journalists, except in the most exceptional circumstances, to protect their sources.

When the source of our stories was identified by police to be freelance journalist Andrew Alderson, his name – along with details of telephone calls and emails between him and MoS News Editor David Dillon – were passed by prosecutors to Chris Huhne’s defence lawyers.

Police files include an entry which reads: ‘Landline attributed to David Dillon for the period 14/11/2011 to 13/11/2012. Checked for contact with all numbers...’

In a bizarre twist, Mr Dillon first became aware that his phone calls had been monitored by police when he happened to notice his own name on a confidential document being read by one of Huhne’s lawyers in a Chinese restaurant near the MoS offices.

In his desperation to wriggle off the hook after illegally passing speeding points to his wife, Huhne would stop at nothing.

Throughout a marathon legal battle to avoid prosecution, the former Energy Secretary claimed this newspaper was engaged in a conspiracy of lies with his ex-wife Vicky Pryce and her friend, lawyer Constance Briscoe, all aimed at disgracing him.

Police officers probing Huhne’s baseless accusations used powers granted to them under anti-terrorism legislation to blithely sidestep a judge’s agreement that Mr Alderson could remain anonymous.

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Mr Huhne's former wife, Vicky Pryce, who was also jailed for eight months after denying perverting the course of justice after she accepted her husbands speeding points on her licence

Officers used RIPA powers – which require only the approval of a senior police officer, rather than a judge – to seize the landline and mobile phone records of Mr Dillon, along with those of Ms Pryce and Ms Briscoe, one of Britain’s first black female judges.

All this time, of course, it should not be forgotten that Mr Huhne knew only too well that he was guilty of the original offence, but he would not admit it until the last possible moment.

By painstakingly cross-referencing the mountain of records, and drawing up a spreadsheet summarising telephone and email contacts, the police established that our source was respected journalist Mr Alderson – then paid him an unannounced visit at his remote home in Cornwall.

Mr Alderson’s mobile and landline records were also trawled through by officers, then they – along with the phone records of the other three parties – were also handed to Huhne’s legal team under the legal process of disclosure, giving the former Lib Dem MP free rein to see what numbers had been called by the very journalists who had been investigating his crime.

Constance Briscoe, a former member of the judiciary, who was jailed for 16 months in May after attempting to pervert the course of justice

THE story of Mr Huhne’s downfall began in September 2010, a few months after he left his economist wife Vicky Pryce, now 62, for press officer Carina Trimingham, 46. Through intermediary Mr Alderson, 56, a Fleet Street veteran, Ms Pryce and her confidante, Ms Briscoe, were introduced to Mr Dillon.

Following a series of meetings, emails and telephone calls stretching over eight months at venues including the houses of friends of Ms Pryce in Clapham, South London, The Mail on Sunday was able to break the story of Huhne’s points switch in May 2011. Huhne was to continue to deny the allegation for almost two years, both in public and to Essex Police, after an investigation was swiftly launched.

On February 3, 2012, the Director of Public Prosecutions, Keir Starmer QC, announced there was sufficient evidence to bring charges against both Huhne and Pryce. At around the same time, the Crown Prosecution Service – and Huhne’s defence lawyers – approached the MoS – for our ‘source material’ relating to the story.

The CPS wanted to use Ms Briscoe as a key prosecution witness against Huhne, but were worried that she had lied to the police, which would discredit her as a witness. And indeed she had, unbeknown to the MoS, by giving a witness statement to the police denying that she had been involved in giving stories about Huhne to the media.

At the same time, Huhne’s team shared the same suspicions and were keen to discredit Briscoe so that her hearsay evidence about what Vicky Pryce had told her about the speeding points could not be admitted to the prosecution case.

In October 2012, the CPS applied to a judge for an order requiring the MoS to produce material which had been provided by Pryce and Briscoe. The CPS application was made under the Police and Criminal Evidence Act (PACE), which acknowledges that journalistic material held in confidence – including the identity of confidential sources – must only be disclosed to the police in exceptional circumstances when very serious crimes are being investigated.

After a legal fight, material was disclosed – but the judge agreed that the name of our source should be redacted from the material.

Soon afterwards, the CPS confirmed that they would drop Ms Briscoe as a witness as she had clearly lied to the police.

Some of Ms Briscoe’s emails which were disclosed to both prosecution and defence referred to her having a ‘police source’. Huhne and his lawyers immediately seized upon this as evidence of a conspiracy against him, and claimed that the prosecution’s case was now fatally flawed.

Mr Justice Sweeney ordered that a different police force should investigate whether Briscoe had compromised the investigation.

That investigation was mounted by Kent Police, under the code name ‘Operation Solar’. But rather than use PACE, the officers decided instead to deploy RIPA, which meant they only needed the authority of a senior police officer to seize landline and mobile phone records and to identify the source, who turned out to be not a police officer at all, but Mr Alderson.

TWO Kent police officers made an unscheduled call to the writer’s five-bedroomed clifftop home in Portloe, Cornwall, on the cold night of November 9, 2012.

POLICE USED TERROR LAWS TO TRACK DOWN SOURCE PROTECTED BY JUDGE An email from 2010, left, with the source's name hidden and Mr Alderson's name being found in Mail on Sunday phone records in 2012 These extracts from a Kent Police document show how detectives trawled through a year’s records from November 2011 for eight phone lines, including the MoS newsdesk, to expose our source. A judge had ordered the MoS to hand over emails stretching further back, but said Andrew Alderson’s name could be redacted. But by obtaining phone records via RIPA, police identified his number and linked it back to the emails. Advertisement

Mr Alderson, stunned to be confronted in this manner, asked the pair why they hadn’t made an appointment.

Their response was that they wanted to see his reaction first-hand. The detectives stressed they wanted to speak to him as a witness, not a suspect, but Mr Alderson sought legal advice and said nothing. A seven-hour drive from Kent had been in vain.

A spokesman for Kent Police defended its use of RIPA, saying: ‘These applications were proportionate, lawful, necessary, recorded and were relevant lines of enquiry for the investigation and the facts were made available to the court and defence.’

A few weeks after the visit to Alderson, in late November 2012, both Kent and Essex Police contacted The Mail on Sunday lawyers to say they had identified Mr Alderson, and when reports were later handed over, it was clear that the officers had painstakingly checked the timing of telephone calls against the redacted emails to piece together the jigsaw.

NONE of which would help Huhne, however.

The judge agreed with the police that there was not – and never had been – any conspiracy, and the prosecution went ahead.

Huhne denied the charges until the day the trial began in February 2013, and subsequently received an eight-month jail sentence, as did his wife, for perverting the course of justice. Later, Briscoe was jailed for 16 months, for attempting to pervert justice.

In our strenuous efforts to protect our sources and resist handing over emails to Huhne’s lawyers, The Mail on Sunday ran up a £150,000 legal bill, none of which can be recovered.

Shortly after emerging from prison, Huhne reflected on the wreckage of his political career and – typically – blamed not himself but the newspapers for his downfall.

Writing in The Guardian of the ‘intrusive and hurtful’ media and the ‘corrosive effect’ on the public’s view of politicians, he seemed to have forgotten the judge’s damning words as he was jailed in 2013. ‘Despite your high office you tried to lie your way out of trouble by claiming you were innocent, by repeating that lie again and again during your extensive interviews by the police,’ said Mr Justice Sweeney.

Last night, when contacted by The Mail on Sunday, Mr Huhne, 60, said simply: ‘Thanks very much’ and ended the call.