An "avalanche" of publicity about Levi Bellfield, which led to the collapse of an attempted kidnap allegation against him, will be referred to the Attorney General.
Mr Justice Wilkie said the material forced him into the "deplorable" position of discharging jurors from returning a verdict in the case.
He said he will ask the Attorney General to consider proceedings against media organisations for contempt of court.
Bellfield faced a charge of trying to abduct 11-year-old Rachel Cowles the day before Milly Dowler disappeared in 2002. But after finding him guilty yesterday of kidnapping and murdering 13-year-old Milly, jurors had yet to reach a verdict on that count.
However, today the judge decided that the media publicity since then had been so prejudicial that the jury could no longer be expected to consider the abduction charge, depriving Rachel of the chance to see her alleged attacker face a jury verdict.
He said: "This is most unfortunate and, in a sense, deplorable. The only person who is going to be affected by what has happened and most affected adversely has been Rachel Cowles and her family. She has had to live for nine years with what happened to her and she has given evidence in court which has no doubt been an ordeal for her.
"As a result of the trigger being pulled too soon on what would otherwise have been proper and appropriate material, I have been put in a position where I am obliged to discharge the jury from reaching a verdict in her case. It is no longer possible for any jury in receipt of this volume and nature of material to give fair and proper consideration to its verdicts at this stage."
The judge said he was not specifying which organisations were responsible, but added: "It does seem to me that at the very least the legitimate question arises, whether by publishing this material these organisations may have committed a contempt of court.
"It seems to me to be inevitable that the court will have to refer this volume of material to the Attorney General for him to have to consider, having viewed the material, whether it is appropriate for proceedings to be taken against any of the news media involved, in respect of what happened."
The judge said some of the material, published about Bellfield after the verdicts, had "strayed" into allegations "of a hugely prejudicial nature", made by others, about the defendant.
Jeffrey Samuels QC, defending, asked for the jury to be discharged on the remaining count, saying that since the verdicts in the Milly case there had been an "avalanche of publicity adverse to the defendant".
"The reader could be forgiven for not realising that this trial is still ongoing and this jury is still deliberating," Mr Samuels said.
Material published included "matters which were excluded from evidence in this trial", such as allegations made by Bellfield's former partners.
Mr Samuels said that nothing the judge could say to the jury would be able to remove the "very real risk of prejudice".
The judge said it would be "unrealistic" to expect jurors not to have been exposed to publicity which was given "great prominence" in national newspapers and on television, and that they had been put in a "hopeless" position.
He said that with "great reluctance" he was discharging them.