Senior figures in his public relations team believe they had their telephones hacked into by Glenn Mulcaire, the private investigator who was working exclusively for the News of the World.
Sir Paul was represented at the time by the Outside Organisation, one of Britain’s biggest entertainment PR companies.
Ironically, the company later employed Neil Wallis, the former deputy editor of the News of the World who was arrested last week, as its managing director. Outside is expected to sever all ties with Mr Wallis later this week.
Outside’s founder, Alan Edwards, and Sir Paul’s personal spokesman, Stuart Bell, who now runs his own public relations company, both allegedly had their telephones hacked during the period when the former Beatle separated from Miss Mills in 2006, after four years’ marriage. The High Court ordered Sir Paul to pay Miss Mills almost £25 million.
It is not thought that Sir Paul was hacked directly because his mobile phone number was known to only a handful of his closest friends, family and advisers.
Mobile numbers for his public relations advisers were readily available.
Mr Bell refused to comment yesterday but sources confirmed he had to change his mobile phone security PIN code on a number of occasions in the period when
the couple’s marriage was disintegrating.
He also discovered messages that had been deleted before he had even heard them and others that had been listened to before he had heard them.
Mr Edwards, one of the most respected figures in the entertainment industry, told The Sunday Telegraph: “Given the line of work I am in and how long I have been in it, I have got to know a lot of people.
“It is unlikely I wasn’t phone hacked. A lot of things were going on during the McCartney-Mills divorce.”
Asked whether stories that appeared in the News of the World might have been as a result of phone hacking, Mr Edwards said stories of the divorce were being published so frequently, he and his team “never had time to think where they were coming from”.
He added: “In retrospect, you have to think it might have been.”
Mr Edwards has been told to expect a telephone call from police informing him he is one of almost 4,000 possible victims of hacking by Mulcaire. So far, fewer than 200 people have been contacted by police and told their names appear in Muclaire’s notebooks.
Mr Edwards refused to discuss the appointment of Mr Wallis, who is listed on Outside’s website as a freelance media consultant in place since 2009.
Miss Mills is also said to be considering suing the News of the World for breach of privacy over alleged phone hacking. It is understood that her name and mobile phone number are also listed in Mulcaire’s notes along with those of her friends and associates. Her sister Fiona, who is her confidante and adviser, is also considering suing News International over alleged hacking.
The couple’s divorce took almost as long as the marriage and was bitterly fought in the High Court. Much of the behind-the-scenes rows were played out in public, including divorce papers leaked to newspapers.
It is not clear what stories might have been obtained as a result of hacking.
Police declined to comment.