Foreign Office official Derek Pasquill had a 20-month wait before discovering whether he would be charged under the Official Secrets Act.
Mr Pasquill is described as 'an extremely brave individual'
He leaked documents which led to articles in the Observer and New Statesman outlining government policy towards radical Islam.
It is claimed that the articles helped spark public debate and influenced the government's engagement with groups such as the Muslim Council of Britain.
The 48-year-old - who remains suspended on full pay from his job as a desk worker in the Foreign Office - was praised by journalist Martin Bright, who called the flood of information "a journalistic goldmine".
On Wednesday, six charges were dropped after prosecutors revealed that internal Foreign Office documents undermined the prosecution case that the leaks were damaging.
Mr Pasquill said he had been through a "very unpleasant ordeal" but he had been "completely vindicated in my actions in exposing dangerous government policy and changing its priorities".
He said it had not been difficult to decide to leak the documents to journalist Martin Bright as the issue was already in the public domain.
"I realised that that is a dangerous way to proceed but this was an issue which was obviously of public interest given the particular circumstances that we are in at the moment in the UK and the world," he said.
"As soon as it clicked that there was perhaps a dangerous policy being put in place, the decision to actually pass documents to a journalist who was covering this particular issue didn't take that long."
Mr Pasquill was working on the Foreign Office approach to "engaging with the Islamic world."
He claimed that the Muslim Council of Britain's moderate image masked what he said were, on closer inspection, more radical views.
The documents he leaked formed the basis for a Policy Exchange pamphlet written by Mr Bright in July 2006.
Ministers had widened the range of Muslim organisations they dealt with since the pamphlet's publication, Mr Pasquill said.
The leaking of e-mails, position papers and policy discussions continued until January 2006 when the civil servant was arrested on suspicion of breaching the Official Secrets Act.
Mr Bright told the BBC News website: "People were unhappy about policy. There were a lot of documents coming out which were deeply embarrassing for the government.
"David is an extremely brave individual. At huge risk he got government policy out, it was legitimate to put it in the public domain. There is an argument that this was a debate which should have been heard in public."
The decision to charge Mr Pasquill led to accusations authorities acted because they were more worried about embarrassing revelations than protecting state secrets.
Mr Bright said none of the documents were marked 'top secret' and all were confidential or less.
There was no suggestion the disclosures put any intelligence agents at risk or jeopardised secret service operations, he said.
"The outrage is he had to wait 20 months until he was charged," Mr Bright said.
The Foreign Office said the leaking of official documents was "absolutely contrary" to good government and hinted that Mr Pasquill could be subject to internal disciplinary procedures.