John Wick said he did fear the consequences of his actions
The man who gave details of MPs' expenses to the Daily Telegraph has insisted that Parliament will benefit from their publication.
Ex-SAS officer John Wick, who passed the data on from an anonymous source, said he had "no regrets" about exposing the expenses system's "rotten core".
He added: "Parliament will be a better place, society will be a better place."
Mr Wick spoke as further allegations about Tory and Labour politicians' expenses were published in the paper.
'A marker down'
Mr Wick said he felt compelled to release the expenses information because the official version that was due to be published in July had lots of details censored.
He said the public had a right to know about MPs' affairs given how much information the government wanted to collect about ordinary citizens.
"Sometimes a marker has to be put down," he said. "The public's put a marker down. It's good."
Mr Wick did not comment on whether the Telegraph paid for the information, but insisted it was not stolen.
It was, he said, "an unregistered copy" obtained "as a result of lax and unprofessional security procedures used in the House of Commons".
"The protective classification given to this project was described to me... as offering the same protection as a wet paper bag," he said.
Mr Wick admitted he did fear the consequences of his actions, but said "sometimes you've just got to step out".
He is a supporter of the Conservatives but said the expenses issue crossed party boundaries, "with some Conservative MPs' behaviour as reprehensible as their Labour counterparts".
The BBC's political correspondent Reeta Chakrabarti said the Metropolitan Police and the Crown Prosecution Service had said Mr Wick would not face any charges as the information is not a threat to public safety and is in the public interest.
Mr Wick, who served in the SAS during the 1970s, now works with a City of London firm that advises insurance companies on how to manage their risk.
'Credibly and reasonably'
His comments came as further MPs were dragged into the expenses row.
The Daily Telegraph reported that shadow business secretary Jonathan Djanogly claimed £5,000 for a set of automatic gates for his home and nearly £13,000 for gardening.
He told the BBC that he had acted "credibly and reasonably", but had decided to repay £25,000 of the £77,104 he has claimed in total because of public anger over expenses.
Jonathan Djanogly said he had acted 'credibly and reasonably'
He said: "I decided - not that I'd done anything wrong, but because of the public dissatisfaction with this whole business, which I share - I would voluntarily give back a significant sum of money. I've also, during this financial year, not claimed a penny."
The paper also accused Northern Ireland Minister Paul Goggins of allowing a university friend to live rent-free in a home paid for by the taxpayer.
But Mr Goggins told the BBC the arrangements were based on a "30-year friendship" with Chris Bain and due to the fact that Mr Bain had been the joint owner of the property for six years between 1997 and 2003.
He added that he would be "happy" for the payments to be examined under new procedures Parliamentary procedures.
The Telegraph also reported that Conservative MP Bernard Jenkin used £50,000 in expenses to pay his sister-in-law rent for the property he uses as his constituency home.
Mr Jenkin told the BBC there was "no suggestion of property speculation" or "phantom mortgages" and that he was just paying "an honest and reasonable rent".
He also said he had himself argued for "sweeping changes" of the expenses system.
"I have devoted my life to public service and I now find myself devastated," he added.
The paper also turned the spotlight on Labour MP Khalid Mahmood for allegedly claiming £1,350 for a stay in a five-star west London hotel with his girlfriend.
Meanwhile, Ian Gibson, MP for Norwich North, has confirmed that he will meet Labour's national executive committee to answer questions about his expenses claims.
He was accused of claiming for a flat in which his daughter and her partner lived. He says he shared the flat for a time.
The Archbishop of Canterbury Dr Rowan Williams has warned that the "continuing systematic humiliation" of MPs threatened to do irreversible damage to public confidence in Britain's democracy.
Writing in the Times, he said: "Many will now be wondering whether the point has not been adequately made."