"It's difficult as a lawyer and as a member of Parliament to find my role to be subservient to masters half my age at the Prime Minister's Office, who tell me how to vote on matters, who tell me what questions to ask of witnesses in committee, who vet my ... one-minute member statements," Rathgeber, 48, told reporters in his Edmonton-St. Albert constituency office Thursday.
"I think legislators like myself have to take a stand ... that we're not going to read these talking points that are written by PMO staffers, that we're not going to vote like trained seals."
Rathgeber announced on Twitter late Wednesday that he was quitting caucus over a lack of government transparency and other concerns.
Rathgeber said he takes Prime Minister Stephen Harper at his word that the PM did not have advance knowledge of a $90,000 cheque written by Harper's chief of staff to assist Sen. Mike Duffy in an expense scandal.
But he said that raises an even more troubling issue.
"It actually creates a much bigger problem, and that is that the Prime Minister's Office seems to be accountable to nobody, not even the prime minister," he said.
"I think that a lot of stuff goes on in the PMO that the prime minister doesn't know about."
Rathgeber also said he finds it "rich" that Andrew MacDougall, a spokesman in Harper's office, has said he should resign and run in a byelection.
"I have two other words: David Emerson. You will recall that in 2006 ... David Emerson, having just been elected days before as a Liberal, walked across the floor and joined the Conservative government.
"The Conservative party doesn't own the seat simply because I won it for them in the last election.
"I'm accountable to my constituents and if I sense that my constituents are unhappy with my decision, then I'll have to deal with it. But the preliminary emails and tweets that have come into the office show anything but unhappiness."
"I'll answer to them. I won't answer to the PMO anymore."
Rathgeber is now sitting as an Independent.
He said he hasn't decided if he will run again, but said if he does it would likely be as an Independent.
"I'll assess the political landscape sometime in 2015," he said.
He said he would be a long shot to win, given the cash and resources available to party candidates.
"I'm most mindful of the difficulty in getting elected as an Independent."
He called his decision to quit a personal one and said he isn't rallying fellow MPs to the barricades.
"I am not trying to break up the government. I'm not trying to break up the party," he said. "I'm doing what's best for me and best for my constituents and that is to resign from a caucus so I can speak freely on issues."
Rathgeber was first elected to the Commons in 2008 and re-elected in 2011.
He said be believed the Conservatives came to Ottawa to clean things up and promote open government and transparency, to be the antidote to the Liberals and their sponsorship scandal.
He said the Duffy affair has proven otherwise.
"When we start justifying and rationalizing that kind of behaviour, I fear we're morphing into what we once mocked," he said.
"I think it's inappropriate at so many levels that the chief of staff to the prime minister would offer a gift to try to make an expense issue go away.
"I think Canadians want to know what was the quid pro quo."
He said the last straw was the government's decision to water down his private member's bill to expose the salaries of senior federal civil servants.
If passed, the bill would have raised the transparency bar for salary disclosure to $188,000. But the committee reviewing the legislation instead decided to raise the threshold to more than $400,000.
He said the Conservative members on the committee were ordered by PMO staffers to raise the threshold, even though not one witness to the committee recommended it.
Reaction to Rathgeber's announcement was mixed.
Newfoundland Liberal MP Scott Andrews praised him for "taking the high road and standing up for your convictions. This place (House of Commons) needs more like you.”
In St. Albert, Sultan Merchant, a retired man out for a walk behind city hall, said Rathgeber took a principled stand.
"The government promised that they would be transparent," he said. "It's nice to see somebody who insists that they should."
Conservative MP Daryl Kramp, from Prince Edward Island, said he respects Rathgeber's decision, but said at some point things still have to get done.
"You can't move in 307 different directions all at once," said Kramp.
"I'm not going to prostitute my principles, of course not, but I'm going to try to operate within the confines of what this institution has stood for all these years."
Note to readers: This is a corrected story. An earlier version said Rathgeber was a first-term MP.