Racing's co-chief stipendiary steward Ross Neal has resigned for personal reasons and to pursue other interests, he said on Monday.
The Racing Integrity Unit (RIU) confirmed the resignation of Neal, whose personal life had been in the public spotlight. The RIU polices the racing industry.
In May, it was revealed he was with Harness Racing New Zealand (HRNZ) employee Lyn O'Connell in a Christchurch motel in February when she suffered a heart attack.
She died in hospital a few days later.
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Her husband, Blair O'Connellā, a Motukarara breeder and trainer, in May called for Neal to resign.
In a statement Neal, who has been in the role for eight years, said he had chosen to resign.
Neal, who recently returned from a period of annual leave, described his decision to resign as "extremely difficult".
"I am and continue to be passionate about the integrity and performance of our industry and believe I have been true to the intent and purpose of my role throughout my time in this role.
Blair O'Connell said in May his wife, licensing secretary for HRNZ, wanted to become a stipendiary steward and told him Neal was helping her with that process.
In fact, O'Connell believed, Neal had taken the opportunity to conduct an affair with her for more than a year.
O'Connell could not be reached for comment on Monday.
Attempts to contact Neal on Monday were unsuccessful. It is unknown what his "personal reasons" for resigning are.
His mobile phone went straight to voicemail.
A recorded voice message said he was no longer working for the RIU and directed all work-related calls to its general manager Mike Godberā.
Godberā said he understood Neal did not wish to comment further.
Godber said he could not comment when asked whether Neal had jumped, or was pushed.
Neal had been an excellent co-chief stipendiary steward and was committed to the industry, Godber said.
Mat Kermeen