Jofi Joseph was director of nuclear non-proliferation on the National Security Council and was helping negotiate nuclear issues with Iran.
But over a period of more than two years he sent hundreds of abrasive tweets under the Twitter alias @NatSecWonk.
He was fired last week after he was caught, a White House official said.
In his Twitter biography, now removed from the social networking site, Mr Joseph described himself as a “keen observer of the foreign policy and national security scene” who “unapologetically says what everyone else only thinks”.
As the widely followed @NatSecWonk, Mr Joseph speculated anonymously about the political motives and career moves of administration officials he worked with.
This month, Mr Joseph tweeted that former secretary of state Hillary Clinton “had few policy goals and no wins” in the Middle East.
More at Topsy.
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Tweets like this: ‘I’m a fan of Obama, but his continuing reliance and dependence upon a vacuous cipher like Valerie Jarrett concerns me.’
— Byron York (@ByronYork) October 23, 2013
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