James Muir-Little, Partner and Head of Family Law Office for Furley Page Solicitors based in Kent and the South East, has resigned as Deputy District Judge during the course of an investigation by the Office for Judicial Complaints.
The investigation was launched following the murder of Millie Hall, 3, by her father Gavin Hall after he discovered his wife, Joanne, was having an affair with Mr Muir-Little.
In November 2006 Gavin Hall was sentenced to a minimum of 15 years in jail at Northampton Crown Court.
Ms Rainsley - she has reverted to her maiden name - and Mr Muir-Little met through a relationship website for married people.
A spokesperson for the Office for Judicial Complaints, said: Mr Muir-Little, a Deputy District Judge on the South Eastern Circuit, has resigned his judicial office during the course of disciplinary proceedings against him, thereby pre-empting any further action. The Lord Chancellor and Lord Chief Justice have accepted his resignation and he will no longer sit as a Deputy District Judge."
A spokesman for Furley Page LLP said: "James has been with the firm for 15 years and is a partner. He immediately offered the Lord Chancellor his resignation as a Deputy District Judge when contacted some time ago; it has taken a significant time for acceptance to be confirmed. We are aware of the difficult time his family has experienced and the effort made to conduct a normal family life."