The latest hearing in the Duke of Sussex’s phone hacking claim against Mirror Group Newspapers (MGN) will be held next week to deal with the consequences of a High Court ruling that saw him awarded a six-figure sum in damages.

Last month, a judge ruled that phone hacking became “widespread and habitual” at the publisher’s newspaper titles, and was practised “even to some extent” during the Leveson Inquiry into press standards.

Mr Justice Fancourt also concluded that the duke’s phone was hacked “to a modest extent” by MGN, awarding him £140,600 in damages.

The judge’s finding that MGN editors knew about voicemail interception and unlawful information gathering prompted ex-Daily Mirror editor Piers Morgan to deny he had ever hacked a phone or instructed anyone else to.

Harry, 39, said his partially successful case against MGN was “a great day for truth, as well as accountability” and called on the police to investigate the publisher of the Daily and Sunday Mirror and The People.

A follow-up hearing dealing with the consequences of the ruling, expected to include the issue of legal costs, is due to be held in London on Monday.

The duke sued MGN for damages, claiming journalists at its publications were linked to methods including phone hacking, so-called “blagging” or gaining information by deception, and use of private investigators for unlawful activities.

In a summary of his ruling, the judge said the duke’s case against MGN was “proved in part only”.

He said that 15 of the 33 articles about Harry examined at trial “were the product of phone hacking of his mobile phone or the mobile phones of his associates, or the product of other unlawful information-gathering”.

The judge ruled that unlawful information-gathering was “widespread” at all three Mirror Group titles from 1996 onwards, and phone hacking became “habitual” from 1998.

He also found that there was still “extensive” phone hacking from 2006 to 2011.

The unlawful activity was “concealed” from Parliament, shareholders and the public, as well as the board overseeing MGN, the judge said.

Harry’s case was heard alongside similar claims brought by actor Michael Turner, who is known professionally as Michael Le Vell and is most famous for playing Kevin Webster in Coronation Street, actress Nikki Sanderson and Fiona Wightman, the ex-wife of comedian Paul Whitehouse.

Claims brought by Ms Sanderson and Ms Wightman were dismissed by Mr Justice Fancourt because they were made too late, despite the judge finding that some of their complaints were proved.

Mr Turner was awarded a total of £31,650 in damages after the judge ruled his phone hacking and unlawful information-gathering case was “proved only to a limited extent”.

Their cases were considered as “representative” of the types of allegations facing MGN and Mr Justice Fancourt’s findings could affect the outcome of other pending claims, which include challenges brought by actor Ricky Tomlinson, the estate of the late singer George Michael, ex-footballer and television presenter Ian Wright and Girls Aloud singer Cheryl.

MGN largely contested the claims and denied that any newspaper articles complained of resulted from phone hacking, while contending that the vast majority did not arise from any other unlawful activity.

An MGN spokesperson said after the ruling: “Where historical wrongdoing took place, we apologise unreservedly, have taken full responsibility and paid appropriate compensation.”