Phone-hacking cases brought by Vic Reeves, Kate Thornton and two others against Rupert Murdoch’s Sun and News of the World have been confidentially settled, just as a six-week trial was due to hear allegations of a cover-up by senior executives at the media mogul’s British tabloids.

The last-minute deal on Thursday earned both sides a rebuke from Mr Justice Mann, who complained that issues important to another 47 hacking cases in the pipeline had not been determined in a case that would have heard allegations of wrongdoing by James Murdoch and Rebekah Brooks.

Instead, a confidential settlement was agreed with comedian Reeves, whose real name is Jim Moir; TV presenter Thornton, Coronation Street actor Jimmi Harkishin and talent agent Chris Herbert. Murdoch’s News Group Newspapers was also expected to pay their costs, estimated at about £4m in total.

The cases had been brought by Jim Moir (better known as comedian and actor Vic Reeves), TV presenter Kate Thornton and Coronation Street actor Rajan Harkishindas, who uses the name Jimmi Harkishin. Photograph: PA

David Sherborne, counsel for the claimants, told the court the claimants would “allege criminality at the most senior level: James Murdoch and Rebekah Brooks” as part of the case.

James Murdoch, the younger son of Rupert Murdoch, was executive chairman of the tabloid’s British owner News UK and is now chief executive of 21st Century Fox, while Brooks has returned to her old job as chief executive of News UK.

The case had also been due to hear allegations of hacking by journalists at the Sun. News UK has never admitted that any hacking took place at the daily title, nor any wrongdoing by senior executives. The last-minute agreement meant neither of these issues were determined.

The News of the World was closed in July 2011 and one its former editors, Andy Coulson, was subsequently found guilty of being involved in hacking at a trial.

Mann noted that Murdoch’s News Group Newspapers had made “admissions of unlawful activity at the News of the World but it has made none at the Sun” in the context of the pre-trial submissions he had received.

Mann also complained that the case had taken years to prepare to reach the trial stage, and that the other litigants in the pipeline had now been deprived of the opportunity to see issues of liability being resolved in a test case.

The judge told the court that the last-minute settlement of the four cases was a “serious matter” because the court had devoted “a significant amount of time and resources” to preparing them for trial due to the perceived importance of the case.

The settlement of a “useful test case raises difficult issues” for others hoping to bring claims, he said, adding that future hacking litigation would have to be dealt with differently.

Ed Miliband, the former Labour leader and a critic of the Murdoch family, said: “This last-minute deal is yet another case of the Murdochs going to extraordinary lengths to prevent detailed scrutiny of what really happened at their newspapers. It shows why we need the Leveson 2 [press] inquiry to get to the truth.”

Rupert Murdoch’s 21st Century Fox is still seeking regulatory approval from the Competition and Markets Authority for a full takeover of the satellite broadcaster Sky, although some opposition politicians, including Miliband, have said the media mogul should be prevented from concluding the deal, partly because of the phone-hacking allegations.

Several other hacking cases, which were not due to come to trial, were also settled on Thursday. They included claims made by the actor David Tennant, and Colin Jackson, the BBC presenter and former athlete.