Former Colour Sergeant Trevor Coult MC launched an attack on the royal after the former soldier quit the UK to move to the US with his wife.
Harry and Meghan Markle, 38, announced in January they would step down as senior royals and have been living abroad for months – with Harry forced to give up his military appointments.
This week the Duke of Sussex joined Meghan to say we must acknowledge the Commonwealth’s “uncomfortable” past as they spoke out about equality.
And ex-Royal Irish Regiment Coult told the Mirror: “He’s turned into a complete idiot.
“His comments are disgusting and I for one am pleased he has left the UK. A lot of soldiers in the British Army are from the Commonwealth too.
“They fought alongside Harry and he should remember that. He’s having a dig at the Royal Family – his own family.
“He says he wants to be left alone to do his own thing but he’s constantly doing Zoom calls.
“He can’t have it both ways so he’s now classed as what I think is an attention seeker. Every time he speaks these days he loses support massively”
“Every time he speaks and insults the Queen, the Royal Family or has a go at the Commonwealth, all that support from all the years is slowly vanishing. It’s sad because he did good work.”
“His comments are disgusting and I for one am pleased he has left the UK. A lot of soldiers in the British Army are from the Commonwealth too” Trevor Coult MC
After the Sussexes stepped down, Harry had to leave his role as Commonwealth Youth Ambassador.
But he and Meghan retained their posts as president and vice-president of the Queen’s Commonwealth Trust.
And this week Prince Harry appeared to reference the British Empire, adding: “There is no turning back now”.
The 35-year-old prince said: “When you look across the Commonwealth, there is no way that we can move forward unless we acknowledge the past.
“So many people have done such an incredible job of acknowledging the past and trying to right those wrongs, but I think we all acknowledge there is so much more still to do.
“It’s not going to be easy and in some cases it’s not going to be comfortable, but it needs to be done, because, guess what, everybody benefits.”
The Commonwealth is formed by almost all countries who were once ruled by the British Empire by Prince Harry’s ancestors.
They made the comments as they took part in the Queen’s Commonwealth Trust video call, one of the network’s weekly sessions set up in response to the growing Black Lives Matter movement.
It comes after Harry last week outlined his personal commitment to tackling institutional racism.