New Zealand jockey Lisa Cropp has apologised for the drug infringement which has halted her latest comeback.

The three-time New Zealand champion was stood down at Te Awamutu on Thursday after she produced a "non negative" sample.

The jockey was involved in a long-running legal battle after returning a positive sample to methamphetamine after riding Darci Brahma to victory at Te Rapa in 2005.

Cropp fought the charge in the Supreme Court but was eventually disqualified for nine months and ordered to pay around $100,000 in fines and legal costs.

She returned to riding and based herself in Melbourne in 2012 before returning to her homeland briefly before announcing her retirement.

The 44-year-old Cropp made her latest return early this month.

In an open letter to New Zealand media, Cropp said she would seek help for her addiction.

"I would like to personally apologise to all my supporters and to all industry participants for my actions during and after my failed drug test at the Waipa Racing Club meeting on Thursday, November 27, 2014," she said.

"With the support of my family and friends I will face this issue head on and get the necessary help and rehabilitation I need to move forward with my life and career in a positive way.

"I am prepared to face a judicial inquiry and abide by any penalties handed to me for my conduct.

"Once again I am sincerely sorry for my shortcomings and behaviour, but am heartened by others that have been able to rise above their addictions and I am determined to achieve this."