Jenny Duggan, an in-demand NSW apprentice who is leading three premiership titles, has been suspended on a running and handling charge.

Duggan was given a one-month ban after Racing NSW stewards on Tuesday completed an inquiry into her ride in a provincial race last month.

Stewards found her guilty of not giving Lady Lonhro the opportunity to finish in the best possible position in a race at Kembla Grange on October 13.

Lady Lonhro was a $4.80 to $3.90 firmer in the Kembla Grange Cup before finishing sixth, beaten three lengths.

Stewards found four main points of concern - between the home turn and the winning post - over Duggan's ride.

Her ban will start after she completes a careless riding suspension from last Saturday's Rosehill meeting.

Tuesday's suspension puts her out of the saddle from December 6 until January 6.

Since switching from the amateur riding ranks, Duggan has been an instant hit, riding winner after winner across the state.

She is a clear-cut leader in the NSW apprentices' premiership and she went to the front in the city title after riding Ollie Vollie to victory on Saturday.

Duggan also leads the NSW provincial premiership for apprentices.