LONDON – British police revealed Wednesday that they would contact thousands of people whose cell phones may have been targeted by the News of The World tabloid, an indication of the scale of the scandal at the heart of Rupert Murdoch’s media empire.

Police have long insisted that only a small number of people were believed to have been spied upon by the tabloid, which employed a private detective to break into the voice mail boxes of the paper’s targets and eavesdrop on their private messages.

But that contention has been challenged by lawmakers, journalists and former employees of the News of The World, who have claimed that the practice was widespread. There also have been allegations that police were hiding the full scale of the phone hacking operation for fear of jeopardizing their relationship with the politically powerful tabloid.

The police have denied those claims, but the force has long been cagey about who exactly was targeted and how many individuals were involved. Alleged victims of the hacking include model Elle MacPherson and actress Sienna Miller, and some have complained that police only gave them evidence reluctantly, fueling allegations of a cover-up.

Police said they were taking a “fresh approach” to informing thousands of people whose names appeared in documents taken from The News of The World’s private investigator, Glenn Mulcaire.

“With this new investigation, we will be as open as we can be and will show them all the information we hold about them, while giving them the opportunity to tell us anything that may be of concern to them,” said Deputy Assistant Commissioner Sue Akers. “In time, we will … make contact with everyone.”

John Prescott, a former deputy prime minister who believes the tabloid used phone hacking to get a story about his extramarital affair, said Akers told him that police now had “significant new evidence” relating to his claim that he had been a hacking victim.

“I now look forward to the police finally uncovering the truth,” Prescott said in a written statement.