Group One-winning trainers Robert Smerdon and Stuart Webb have agreed to stand down pending an inquiry into charges relating to race day treatments.

The two train under the umbrella of the Aquanita management company and their horses will be dispersed among Robert Hickmott, Henry Dwyer, John Sadler and Nick Ryan at Caulfield from next week.

Racing Victoria stewards have also charged trainers Tony Vasil and Liam Birchley and asked them to show cause why they should not be stood down.

Four others face charges with Smerdon employees Denise Nelligan and Daniel Garland also standing down and Glen Nelligan asked to show cause.

The eighth person charged, trainer Trent Pennuto, a former employee of Vasil, is already serving a disqualification for a similar offence.

The investigation was sparked by the alleged race day treatment of the Smerdon-trained Lovani at Flemington on October 7, and uncovered more than 200 such incidents dating back to 2010.

Vasil and Queensland trainer Birchley previously trained under the Aquanita name and have until January 22 to prepare submissions regarding the show case notices.

Having stood down, Smerdon, Webb, Nelligan and Garland will be under the same restrictions as suspended licensees.

Aquanita chairman Peter Howell said in a statement the organisation would consult with Smerdon and Webb as well as owners to determine where the horses would go.

"As well as contacting owners to advise them of this decision, we are in the process of allocating training responsibilities to Rob Hickmott, Henry Dwyer, John Sadler and Nick Ryan," Cowell said.

"With these multiple Group One winning trainers, we have every confidence the horses trained by Robert and Stuart will receive outstanding training and care.

"As part of the transition, we will provide owners with options and advice regarding the most suitable trainer for their horse, with guidance from Robert and Stuart.

"The most important point is that every horse will receive outstanding care and training, irrespective of their trainer. We are aiming to have this transition completed by 22 January."

Cowell added the Aquanita brand would be discontinued and the company would function under another name.