Four private detectives have been given jail terms for conspiring to defraud people by "blagging" personal information via persuasive phone calls.
Daniel Summers, 32, Philip Campbell Smith, 53, Graham Freeman, 51, and Adam John Spears, 72, had pleaded guilty to the charges at earlier hearings.
Summers talked banks, building societies and phone firms into revealing confidential details.
The four were working for private companies, solicitors and individuals.
Smith is also the subject of a separate computer hacking investigation.
The men were sentenced at Kingston Crown Court for the offences, which took place in various parts of England and Wales between January 2007 and May 2009.
Summers, of Kingston on Thames, was given two 12-month sentences - to run concurrently after pleading guilty to two of the fraud offences, while Freeman, of Spain, was given a six-month sentence.
Spears, of Biggin Hill, and Smith, of Northampton, received eight-month custodial sentences.
Smith, who had at one time served in Northern Ireland with the British army's special forces, also received four months, to be served concurrently, for possessing a small amount of ammunition.
The case was the result of a long-running inquiry by the Serious Organised Crime Agency (Soca) focusing on the illegal practice of "pretexting", commonly known as "blagging".
Soca put Smith, a co-director of private detective agency Brookmans International, under surveillance. The organisation also had information that Summers possessed a personal computer which could have "information about criminal activity stored on it."
In 2008 a Soca officer answered an online advert to buy Summers' Apple computer. From its hard drive - which Summers had failed to wipe properly - computer forensics experts were able to obtain dozens of incriminating emails and other documents.
They showed he had been working for three other private investigators - Smith, his colleague Freeman, and retired Metropolitan Police detective Spears.
They had commissioned him to obtain confidential details using his blagging skills.
In one case Freeman and Smith tasked Summers with targeting a family-owned property developing firm.
Summers managed to obtain the maiden name of the mother of the owners, her place of birth, detailed transactions from at least four bank accounts, information about a credit card account and a mobile phone account.
Summers charged the two private detectives £200 for each one-month bank statement he obtained and £50 for "credit card trawls".
They, in turn, were paid more than £14,000 by their client - a company which had asked for the information.
Soca has refused to disclose the identity of the "client" in this case.
However, the court heard the company commissioning the investigation was a currency broker; Hailwood International Foreign Exchange - which was owed money by the property developers in question.
The judge said there were grounds for believing the "targets" were involved in illegality themselves, along with others the private detectives were interested in. Norfolk police have confirmed they are investigating.
Soca has said there is no evidence the "client" knew the information would be obtained illegally.
During mitigation hearings, Summer's barrister said his client had been an alcoholic and described him as "a fragile man". Summer's partner, who gave birth last June, cried in the public gallery of the court as his sentence was handed down.
Spears, who had set up Global Intelligence Services Ltd, following his retirement from the police, was described by the judge - Andrew Campbell - as having had a "good career" with the Metropolitan Police and as having served the community well by fostering children with his wife.
The judge said Freeman, who was also a co-director at Brookmans International, had been less involved than Smith.
He said two of the three investigations used in evidence against him were into people "you had good reason to believe had committed serious crime".
But the judge added: "You knew the investigation was being made in a way that was criminal".
Before his sentencing, Freeman had told the BBC he and Smith had been targeting individuals and companies who had committed fraud.
They had been working for the victims of the fraudsters who wanted to get their money back.
This, he said, justified breaking the law, because the police "weren't interested" in helping.
Meanwhile, it has been revealed that Smith is also under investigation for hacking computers, allegedly on one occasion to obtain information for the News of the World.
A source familiar with the investigation says allegations about Smith's involvement with computer hacking first surfaced in 2005.
The BBC's Panorama programme has revealed Philip Campbell Smith hacked the computer of a former army intelligence officer, Ian Hurst, in 2006 in an attempt to get information about an IRA informer for the News of the World.
Mr Hurst claims Soca and the police had evidence of this and other hacking in 2007 but did not tell him he had been targeted. Soca has not responded to the allegation.
The Metropolitan Police is investigating further, and has recently increased the number of officers involved.
Mr Hurst says computer hackers could get access to far more personal information than the phone-hackers or blaggers currently the focus of public attention.
"If you were to quantify it from a damage point of view, well phone-hacking would be down at one, while computer hacking would be up there at 10."