Kathy Griffin has sparked outrage after suggesting President Donald Trump be injected with a potentially-fatal syringe.

The outspoken comedienne - who caused a huge backlash in 2017 when she tweeted an image of herself and what looked like the bloodied head of the president - suggested the US leader be subjected to an injection of ''nothing but air'', a procedure that could cause a lethal blood vessel blockage caused by bubbles or air or gas in the circulatory system.

Kathy was responding to a tweet that said the president had been at a White House diabetes event and asked: ''I don't use insulin. Should I be?''

She replied: ''Syringe with nothing but air inside it would do the trick. F**K TRUMP.(sic)''

The Washington Examiner newspaper pointed out the action could be fatal but Kathy remained defiant.

The paper's account posted: ''.@KathyGriffin advocates for someone to stab @realDonaldTrump with syringe full of air.

''Air embolisms, caused by air getting into the bloodstream, can be fatal.''

Kathy replied: ''I SURE DID, F---ER.(sic)''

After her controversial photoshoot with the Trump head, the 59-year-old star lost endorsements deals, her tour was axed and she was dropped from her role as co-host of CNN's New Year's Eve coverage with Anderson Cooper due to the controversy.

The star was also put on the no-fly list until the FBI investigation into her was completed.

She previously said: ''Trust me, there are times when I want to distance myself from that photo, but it really is a First Amendment issue.

''They were thinking of charging me with conspiracy to assassinate the President of the United States, because I look like the typical ISIS member, right?''

And she was also sent death threats as a result of the controversial pictures.

She said: ''I admit for two days I was on a ball on the floor sobbing and yes, I had a horrible press conference and all that other stuff made it worse... everyone turned on me, left and right.

''On the one hand, I was being investigated by the feds, and on the other hand, I was getting calls from the FBI saying, 'OK, you're under a legitimate and what they say credible threat,' so a lot has happened.''