Lawyer Neil O'May makes a statement on behalf of his client Christopher Galley
The solicitor for the Home Office worker who leaked information says he did it because it was material that was "important for the public to know".
Christopher Galley's lawyer added: "If ever there was a case of don't shoot the messenger, this is surely it."
The 26-year-old was arrested and held for 17 hours by police on 19 November.
Solicitor Neil O'May said Mr Galley had first met shadow immigration minister Damian Green, who was himself arrested last week, in 2006 in parliament.
Mr O'May, of Bindmans solicitors, speaking at a press conference with Mr Galley sitting beside him, said the civil servant was unable to speak as he was still under active investigation.
He claimed his client's arrest had been "unpleasant and unnecessary" and that the documents leaked were not of major importance in terms of national security.
'Open and democratic'
Mr O'May also denied newspaper reports that Mr Galley had been knowingly used by police after his arrest in an attempt to entrap Mr Green.
He said: "Mr Galley gave Damian Green information which was important for the public to know in an open and democratic parliamentary system.
"As a shadow minister for immigration and as a Member of Parliament, Damian Green received the information in the same spirit and used it in his parliamentary duties.
"In providing this information for a shadow minister, Mr Galley believed that it would be used in a highly responsible manner in the public interest."
Mr O'May also said: "Those who initiated the police investigation and those who sanctioned the use of these powers of arrest and search against a civil servant who was giving information directly to an MP should consider whether this was a necessary and proportionate way of dealing with this kind of allegation."
He insisted the leaked documents were "embarrassment material" and important to holding the government to account.
Mr O'May said: "It's really not state secret, national security, terrorism, financial jeopardy, loss, gain or otherwise - nothing remotely like that."
Mr Galley has not been charged with any offence and has been bailed to return to police in January.
Mr Green, MP for Ashford, was arrested on Thursday on suspicion of conspiring to commit misconduct in a public office. He has denied any wrongdoing and has also not been charged.
Police held him for nine hours last week and allegedly accused him of "grooming" the civil servant to pass on information.
Mr Green's homes and offices were searched.
Mr Galley was a Conservative activist and is believed to have previously applied for jobs in Mr Green's office.
There is Tory anger over the police's alleged use of the term "grooming" because it is usually mentioned in relation to child sex offences.
But one senior police officer has defended the Metropolitan Police's handling of the case against accusations of heavy-handedness.
No one can be above the law
Ken Jones, Chief Constable of Sussex
Ken Jones, chief constable of Sussex Police force and president of the Association of Chief Police Officers, urged people to "suspend judgement" about the case and let the police continue their inquiries.
"No one can be above the law," he said. "The good reputation of our Parliament turns, to an extent, on its willingness to demonstrate its support for the principle when necessary."
The fact that the Home Office handles sensitive information affecting the security of the country must be taken into account when considering the nature of the investigation, Mr Jones added.
"To meet that responsibility in a way which delivers effective law enforcement to the people of our country requires complete trust between government, law enforcement and intelligence agencies.
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