A senior White House national security official has been fired after being unmasked as the voice behind a Twitter account that was critical of the Obama Administration.

As director of nuclear non-proliferation, Jofi Joseph was helping to negotiate nuclear issues with Iran. But for more than two years, he also sent hundreds of tweets, many of them containing personal insults, using the Twitter handle @NatSecWonk, said the Guardian.

The White House has confirmed that Joseph was fired last week but has declined to comment further.

An administration official told Politico that Joseph had been about to move from White House duty to a senior role in the Pentagon.