A total of 5,795 people may have had their phones hacked by the News of the World (NoW) newspaper, police now say.
The figure was "very likely" to be revised in the future following further analysis, the Metropolitan Police said.
In July, police said they had gathered material containing 3,870 first and second names of people whose phones could have been illegally accessed.
The NoW was shut down in July after it emerged phone hacking could have been more widespread than initially thought.
News of the World (NoW) journalist Clive Goodman and private investigator Glenn Mulcaire were jailed in 2007 after admitting the practice, which was portrayed at the time as the work of a rogue reporter.
In a statement issued on Thursday, the Met said: "Operation Weeting continues to analyse relevant material.
"It is not possible to give a precise figure about the number of people whose phones have actually been 'hacked' but we can confirm that as of today's date the current number of potentially identifiable persons who appear in the material (and who may therefore be victims), where names are noted, is 5,795."
New core participants
Tony and Cherie Blair's former lifestyle consultant Carole Caplin is the most recent person to emerge as a possible victim.
A spokesman said police had notified her that her mobile phone messages had allegedly been hacked by Mulcaire.
Prime Minister David Cameron has set up a judicial inquiry into phone hacking, with hearings due to begin on 14 November.
Lord Justice Leveson will lead a seven-strong panel, which is expected to report on the culture, practices and ethics of the press within 12 months.
It was announced on Thursday that the judge had agreed to requests by singer Charlotte Church and former Crimewatch presenter Jacqui Hames to be core participants in the inquiry.
Fifty-three alleged victims have now been granted core participant status, meaning they can be represented by a barrister, seek to cross-examine witnesses and make opening and closing statements during the inquiry.
Other core participants include author JK Rowling, actors Hugh Grant and Sienna Miller, and the family of murder victim Milly Dowler.
It emerged in June that someone working for the NoW had accessed Milly's messages after she disappeared in 2002.
This revelation led to the decision to close the NoW.
News Corporation chairman Rupert Murdoch confirmed last month that the Dowler family would receive a £2m settlement relating to the hacking.
The payout is believed to be the biggest so far to NoW hacking victims.
Mr Murdoch said he would also give £1m to charities chosen by the Dowlers, to underscore his regret at the "abhorrent" behaviour.
A number of other high-profile figures have taken legal action against News International - the News Corporation subsidiary which owned News of the World - with a group of claimants due to give evidence to a High Court judge in January.