Prince Harry has spoken out about the "deeply troubling" rise in anti-Semitism in the UK in a new opinion piece.

The Duke of Sussex stressed the importance of "legitimate protest", adding that he felt compelled to speak out because in his view standing on the sidelines allows "hate and extremism to flourish unchecked".

Writing in Britain's The New Statesman, he referenced recent lethal violence against the Jewish community in Manchester and in London and said "hatred directed at people for who they are, or what they believe, is not protest. It is prejudice".

Harry also wrote about the "deep and justified alarm" at the scale of loss in Gaza and Lebanon but argued people must be clearer about where their anger is directed.

"We have seen how legitimate protest against state actions in the Middle East does exist alongside hostility toward Jewish communities at home - just as we have also seen how criticism of those actions can be too easily dismissed or mischaracterised," he wrote.

"Nothing, whether criticism of a government or the reality of violence and destruction, can ever justify hostility toward an entire people or faith."

He said he had learned from his own past mistakes.

In 2005, at the age of 20, Harry was photographed wearing a Nazi uniform to a party.

The piece is critical of the lack of nuance in much of the media discourse in the wake of the recent spate of anti-Semitic attacks in the UK.

The duke bemoans how polarised public debate has become, and said it deepens the confusion that "fuels division".

Harry acknowledged that the instinct to speak out, march and call for an end to suffering was "human and necessary" but people must be clear that the "onus falls squarely on the state - not an entire people".

Referencing the actions of "the state" throughout the piece, he at no point named Israel.

"We cannot ignore a difficult truth: when states act without accountability, and in ways that raise serious questions under international humanitarian law - criticism is both legitimate, necessary and essential in any democracy," Harry wrote.

"The consequences do not remain contained within borders. They reverberate outward, shaping perception, inflaming tensions."

Harry concluded his piece with an appeal for unity and a call for people to stand against anti-Semitism and anti-Muslim hate wherever it appears.

"When anger is turned towards communities - whether Jewish, Muslim, or any other - it ceases to be a call for justice and becomes something far more corrosive," he wrote.