Prince Harry and six other claimants could face a legal bill of up to £34.5m after losing a privacy case against Associated Newspapers Limited (ANL).

The seven claimants, including Sir Elton John, David Furnish, Liz Hurley, Sadie Frost, Sir Simon Hughes and Baroness Lawrence, have been ordered to pay an initial £9.54m to ANL by Friday next week.

Mr Justice Nicklin ruled that the case was unusual because the claimants could be required to pay significantly more than the costs previously agreed before the trial. He criticised the way the claims were presented, describing them as “unreasonable to a high degree”.

On 7 July, the judge dismissed claims that ANL had unlawfully gathered private information. The newspaper group had denied the allegations.

The claimants have until 2 October to seek permission to appeal the ruling.

The group had insurance covering up to £16.2m of ANL’s legal costs if they lost the case. However, Friday’s ruling means ANL could seek to recover up to £34.5m that it says it spent defending itself.

As a result, Prince Harry and the other claimants could potentially face an additional bill of around £18m beyond their insurance coverage.

Justice Nicklin said the claim for costs exceeding £34m appeared excessive and raised concerns about whether all of the costs claimed by Associated Newspapers had been reasonably incurred and were reasonable in amount.