Damian Green told BBC Two's Newsnight of the threat of life in prison
The Tory MP arrested during an inquiry into Home Office leaks says police told him he faced life in jail if convicted of misconduct in a public office.
Damian Green told the BBC he thought it "absurd" when officers told him it could lead to life imprisonment.
After a five-month inquiry it was announced the leaks were not damaging enough to bring any charges.
Home Secretary Jacqui Smith has said it would have been "irresponsible" for the police not to have taken action.
Mr Green was arrested in November and held by the Metropolitan Police for nine hours on suspicion of "conspiring to commit misconduct in a public office, and aiding and abetting, counselling or procuring misconduct in a public office".
He was accused of receiving leaked information from Home Office worker Christopher Galley, who was also arrested as part of the investigation.
But the director of public prosecutions, Keir Starmer, announced on Thursday that the leaked information was not damaging enough for charges to be brought against either man involved.
Mr Green and Mr Galley have always denied any wrongdoing over the leaks which related to immigration and crime.
Asked about the warning of life imprisonment on Newsnight, Mr Green said: "I assume it's because it's a common law offence therefore because there is... no law on the statute book which I was alleged to have broken, then presumably there is no set sentence for it.
"I just thought this was absurd."
Mr Galley told the Daily Mail police said the same thing to him.
Mr Green earlier said he was "very pleased" at the decision not to bring charges over the leaks, but called the government "out-of-touch and authoritarian".
But former Lord Chancellor Lord Falconer said Cabinet Office guidance when sensitive information had been leaked was to consider calling in the police. Keir Starmer's decision had effectively limited the circumstances in which they could now be called in, he said.
He told BBC Radio 4's Today programme: "In a way, it's cutting off at the pass any repeat of the Damian Green-type issue."
The Ashford MP's home and his offices in Kent and in the Houses of Parliament were searched as part of the inquiry.
The parliamentary search took place without a warrant and led to calls for Commons Speaker Michael Martin's resignation.
MPs from all parties also complained the arrests and subsequent searches could undermine the ability of politicians to hold the government to account and raised concerns about the confidentiality of information held about constituents.
Ms Smith, who is already involved in a row about her use of Parliamentary expenses, has defended the decision to call in the police when internal Home Office investigations failed to find the source of the leaks.
Defending her against newspaper reports suggesting her job was on the line, Home Office minister Vernon Coaker told Sky News she was doing a "good job" and it was a "privilege" to work with her.
She was getting on with the job of tackling crime and keeping the country safe, he added.
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