Premier Denis Napthine has been unable to shake controversy surrounding his decision to spruik once-disgraced bookmaker Rob Waterhouse, and his involvement in a Liberal Party fund-raiser headlined by Gai Waterhouse at next week's Warrnambool races.

The Premier has vehemently denied there is a conflict of interest in him supporting Mr Waterhouse to work in the betting ring - he is allowed to work elsewhere at the event - and the fact Ms Waterhouse is the star attraction along with Dr Napthine at a Liberal Party branch fund-raiser next Wednesday night.

On Thursday Dr Napthine said the $100-a-head event had been arranged by a third party. The Premier's office said the third party was "a racing enthusiast".

It is understood that Tim Auld, a racing columnist for The Standard, approached Dr Napthine at last year's Spring Racing Carnival saying that he thought Ms Waterhouse would be interested in appearing at a function for the Premier during the Warrnambool carnival as she was going to be in town.

The Premier said yes and Mr Auld later confirmed the event.