Queensland apprentice Luke Tarrant has been disqualified for six months after returning a positive swab to an illegal drug.

At an in-camera inquiry at Racing Queensland's headquarters on Wednesday, Tarrant pleaded guilty to having a cocaine derivative in his system during a race meeting.

The 21-year-old Tarrant was stood down from riding on Christmas Eve after a random drug test at Ipswich early last month returned a positive.

The B sample was returned last Friday, confirming the original finding.

Chief steward Allan Reardon said the inquiry had been held in-camera to allow Tarrant could raise personal matters.

Tarrant was among the top riders in Queensland last season and won the Group Two ATC Villiers Stakes on Rudy and the Magic Millions 2YO Classic on Le Chef.

He was suspended for a month after his ride in the Group Three Grand Prix Stakes in May and struggled to have an impact after returning to riding.