This is an increase of six per cent since May last year, when roughly half (58 per cent) of those polled said they had a negative view of the prince.
Meanwhile, the latest poll shows that only one in four (26 per cent) of Britons have a positive view of Harry.
His net favourability among Britons is currently at an all-time low of minus 38, with his wife, the Duchess of Sussex, achieving a score of minus 42.
The findings follow another poll conducted by YouGov earlier this year, which found that 65 per cent of adults in the UK were “not interested at all” in the release of Harry’s forthcoming tell-all memoir, Spare.
The book is officially released on 10 January but was accidentally published earlier than expected last week in Spain.
The poll found that just four per cent of those surveyed were “very interested” in the book, while 11 per cent were “somewhat interested”.
On Sunday, Harry conducted two interviews to promote the publication of his book, one in the US and one in the UK with ITV’s Tom Bradby.
In the latter, the prince opened up about his relationship with the media, his decision to step down from the royal family, and tensions with his brother, the Duke of Cambridge.