Comedienne Kathy Griffin has said she has been "exonerated" over a stunt in which she posed with a fake bloodied and decapitated head resembling Donald Trump.

The 56-year-old revealed she is no longer under investigation after the case against her was dropped.

Writing on Twitter she said: "I am no longer under federal investigation. The case is closed, I have been completely exonerated. Finally."

The image, which Griffin shared on Twitter, resulted in a public backlash with Donald Trump Jnr, Chelsea Clinton and the US president himself reacting with outrage.

"This is vile and wrong. It is never funny to joke about killing a president," Chelsea, daughter of Hillary and Bill Clinton posted on Twitter.

Potus slammed the image as "sick" and said that his 11-year-old son Barron "was having a hard time" after seeing the image of the bloodied head that resembles his father. First Lady Melania Trump called the image "very disturbing".

The photo was taken by inline skater-turned-photographer Tyler Shields who is known for his outrageous and often politically incorrect photo shoots. "We have to move to Mexico today, because we're going to federal prison...we're not surviving this," Griffin said in a behind the scenes video from the shoot.

The comedian publicly apologised for the stunt and asked photographer Tyler Shields to remove the images, but a Secret Service investigation was launched.

Seeing the error of her ways and possible legal ramifications, Griffin took down the insulting images from her account and replaced them with an apology video as she admitted she 'went too far."

"I sincerely apologise. I am just now seeing the reaction of these images. I'm a comic. I crossed the line. I move the line and then I cross it," she said. "I went way too far."

"The image is too disturbing. I understand how it offends people. It wasn't funny," the actress added. "I get it. I've made a lot of mistakes in my career. I will continue. I ask your forgiveness. Taking down the image. Going to ask the photographer to take down the image.

"And I beg for your forgiveness. I went too far. I made a mistake and I was wrong."

Following the backlash Griffin suffered a series of professional losses. Five tour dates were cancelled and she lost her endorsement deal with Squatty Potty. She was also been fired from her role hosting the NYE celebrations for CNN.

At a press conference in June Griffin said she was the first entertainer "in history" to be hounded by a president."They are using me as the shining object so no one talks about his FBI investigation," said Griffin.