Lord Justice Leveson has called on the press to give evidence on which journalists used private investigator Steve Whittamore.

The judge said newspaper groups had until September 10 to reveal which of their journalists commissioned the investigator – the source of the Operation Motorman files – to obtain personal data and what happened to that information.

The inquiry is likely to sit again in August for a hearing on evidence relating to Operation Motorman. Lord Justice Leveson said he expected more evidence to emerge from submissions, the Motorman hearing and police investigations but it was “comparatively remote” the inquiry would hold more public hearings.

Newspaper publishers will be served with letters, under rule 13 of the Inquiry Rules 2006, informing them of any criticism of their titles in the inquiry’s final report, due in the autumn.

The judge warned newspapers against publishing these letters as “emerging thoughts”, saying to do so would “misunderstand the purpose of the exercise and the position of the inquiry”.

Press reports of the inquiry will continue to be added to official evidence until the final report is submitted to the culture secretary and home secretary.

The judge added: "I will consider reports that in my view either support or undermine concerns that have been expressed in evidence, I will equally considered the validity of the comments that are critical of the direction or approach of the inquiry."

Lord Justice Leveson also invited Lloyd Embley, editor of the People, to respond to claims made by Matt Sprake of NewsPics picture agency last week. The inquiry heard how Sprake had been commissioned hundreds of times to follow and photograph public figures and celebrities – largely by the People and the News of the World.