Judge Matthew Nicklin's judgment on costs, which was published on Friday, also ordered an interim payment from the claimants of 9.54 million pounds ($A18.26 million) towards the legal costs of Associated Newspapers.
Last month, judge Matthew Nicklin comprehensively rejected the case brought by King Charles' younger son, John and five other figures, rejecting allegations that the Mail titles had engaged in widespread unlawful activities such as phone hacking.
Friday's judgment delivered a damaging blow to Harry and the others by ruling that the outstanding amount should be paid on an "indemnity basis".
This means that as the losing party the prince and the others must pay towards Associated's costs without the publisher needing to show these were reasonable and proportionate.
Explaining his decision, Nicklin was highly critical of the way the claimants' case had been put, including that serious allegations had rested on "speculative and inferential" foundations.
"In my judgment, the cumulative effect of these matters takes the case well outside the norm. The conduct was unreasonable to a high degree," Nicklin said.
A spokesperson for Harry did not immediately respond to a request for comment.
A spokesman for Associated Newspapers called the ruling "another overwhelming victory for the Mail and its journalism".
The court was told at a hearing in July that Associated had incurred a legal bill of 34.5 million pounds while Harry and other claimants only had an insurance policy which covered 16 million pounds.
Associated's lawyer Antony White argued the claimants had made wide-ranging and serious "egregious" allegations without supporting evidence which had added to their costs.
He also said Harry's statement following the ruling was an abuse of his position and celebrity status.
Nicholas Bacon, the lawyer for the claimants, said in their submissions that Associated's 34.5 million pound legal bill was "eye-watering," far exceeding an agreed budget.
