Jodie – who was in America at the time – posted the picture on the same day as a 12-year-old fired gun shots, injuring two class mates, at his school in New Mexico.
The picture was posted along with the caption: ‘Only in the USA’, leading to outrage among users.
One user wrote: “Goes on about anti bullying but finds it ok to stand there with a gun in her hands, in a country that has had more kids killed in schools/colleges than any other country. Bit f***** up if you ask me. Aint gonna do her image any good.”
Another posted: “Stupid behavior that makes you look like a gang member wannabe. Why would you want to look like a thug?”
During the school shooting, a 12-year-old boy and a 13-year-old girl were injured and taken to hospital. Both are said to be in a critical condition.
Jodie, who is filming a new TV show in America, defended her actions to a UK newspaper. She said: “I’m not encouraging people to go out and buy a gun and hurt anybody.
“It’s ridiculous to say I’m trying to glamourise guns – I wouldn’t hirt anybody with my hands let alone a gun.
“I probably know more about school shootings than most of the British public because I have researched it. The gun in the picture belongs to an ex-military man who has a collection of 53 guns who I met yesterday as a part of a TV show I’m working on.”