New York: A longtime national security analyst for Fox News has told colleagues he is done with the network which he says has become "a propaganda machine" for President Donald Trump.

Retired Lieutenant-Colonel Ralph Peters said in an email, first reported by BuzzFeed, that he chose not to renew his contract as a paid contributor with Fox News on March 1 because he was "ashamed" of the network.

He said the 21st Century Fox-owned cable channel has gone from being a valuable conservative voice to "assaulting our constitutional order and the rule of law, while fostering corrosive and unjustified paranoia among viewers."

Peters' comments directly targeted the network's opinions hosts - which include Tucker Carlson, Sean Hannity and Laura Ingraham - for their consistent attacks on special counsel Robert S. Mueller III's investigation into Russia's interference with the 2016 presidential election. Mueller is also looking into whether Trump obstructed justice when he fired James B. Comey from his post as FBI director.

"When prime-time hosts - who have never served our country in any capacity - dismiss facts and empirical reality to launch profoundly dishonest assaults on the FBI, the Justice Department, the courts, the intelligence community (in which I served) and, not least, a model public servant and genuine war hero such as Robert Mueller - all the while scaremongering with lurid warnings of 'deep-state' machinations - I cannot be part of the same organization, even at a remove," Peters wrote. "To me, Fox News is now wittingly harming our system of government for profit."