Tabcorp bookmaker Sally Snow has been warned off for failing to produce her mobile phone to Racing NSW stewards as part of an investigation into betting activities.

Snow is reported to have resigned from her position as the TAB's senior trading manager - thoroughbred trading fixed odds betting on Wednesday, the same day she was sanctioned.

Racing NSW said Snow was repeatedly directed to produce her mobile telephone(s) to the stewards in relation to an investigation and inquiry into betting activities.

She refused on the basis she wished to assert her common law privilege against self-incrimination and also informed stewards she intended to assert common law privilege against self-incrimination and not provide any information or evidence at any inquiry.

Snow was repeatedly told she would be sanctioned with the possibility she would be warned off if she did not co-operate.

"Racing NSW has zero tolerance for those that obstruct and hinder the maintenance of the integrity of thoroughbred racing in New South Wales," Racing NSW chief executive Peter V'landys said.

"We have set a precedent in warning off, and/or excluding from participation, those persons that jeopardise the integrity of racing and it is important that we maintain that strong stance.

"Even though Mrs Snow has refused to cooperate, we will continue to pursue the matter to ensure the integrity of thoroughbred racing has not been compromised,"

Warning off means a person cannot enter any racecourse or training facility, cannot have an interest in any thoroughbred racehorse and is not able to place a bet on thoroughbred races with a wagering operator.