Cherie Blair will not be disciplined after she was cleared over comments she made while sparing a violent offender jail.
Several complaints were made over a case Mrs Blair dealt with while sitting as a judge at Inner London Crown Court.
She told devout Muslim Shamso Miah he would not go to prison after breaking a man's jaw "based on the fact you are a religious person".
The comment provoked a complaint from the National Secular Society, who said it was "discriminatory", as well as several others who read media reports.
Mrs Blair, wife of former prime minister Tony Blair, was sitting as a part-time judge using her maiden name Cherie Booth.
The Office for Judicial Complaints said an inquiry was launched after "a number of complaints" were made about "comments reportedly made" by Mrs Blair.
A spokeswoman said: "That investigation has concluded and found that Recorder Booth's observations did not constitute judicial misconduct.
"The Lord Chancellor and Lord Chief Justice have considered the conclusions of the investigation and agree that no disciplinary action is necessary."
Miah, 25, was jailed for six months, suspended for two years, after the attack in a bank queue in East Ham, east London, when he appeared in court in February.
Terry Sanderson, president of the National Secular Society, criticised the inquiry into Mrs Blair's actions which he said lacked transparency.
He said: "We hope this episode will serve as a reminder to the judiciary to treat everyone before them equally, regardless of their belief or lack of it, and never to act in a way that might give the perception that this might not be the case.
"We believe we should be informed about how Cherie Booth QC explained the remarks attributed to her, and the basis of the conclusions reached by the Lord Chancellor and Lord Chief Justice.
"In the absence of such information, we are unable to comment on their decision."