On the same day Darren Smith lost his appeal against a 15-year ban for cobalt offences, the vet at the centre of cobalt inquiries in Sydney and Melbourne has admitted to providing bottles labelled "vitamin complex" to three trainers.

Tom Brennan, a partner at the Flemington Equine Clinic, on Wednesday made several admissions to Racing NSW and Racing Victoria stewards, telling them the initial evidence he gave was not "full and frank".

He has confirmed to Racing NSW stewards that he did give two bottles of an injectable substance labelled "vitamin complex" to Sydney trainer Sam Kavanagh and accepted two payments of $1000 for them.

Brennan originally denied he was the supplier.

He has also admitted to disposing of an exercise book which recorded postage details of the two bottles to Kavanagh.

Brennan has also come clean to Victorian stewards, admitting he administered "vitamin complex" in an intravenous drip to horses trained by O'Brien and Mark Kavanagh last spring.

He said the two Melbourne trainers paid him $3000 for the substance, which Brennan alleged he forwarded as payment to another vet.

However, Mark Kavanagh has denied paying Brennan while O'Brien has disputed some aspects of Brennan's evidence concerning the payment.

While Brennan has admitted his involvement in the saga which has rocked the racing industry, the vet is adamant he did not do so knowingly.

He has told stewards that the vet who gave him the bottles of "vitamin complex" assured him it contained no prohibited substances, including cobalt.

Racing NSW has since interviewed the vet named by Brennan and are continuing to pursue that line of inquiry.

Racing Victoria stewards are also delving deeper.

Brennan has agreed to stand down from practising on racehorses from August 1, pending the outcome of charges against him.

Brennan will front Racing NSW stewards early next month over 11 cobalt charges stemming from the inquiry into the Sam Kavanagh-trained Midsummer Sun's positive swab to cobalt and caffeine following its Gosford Cup win in January.

Sam Kavanagh will have 24 cobalt charges against him heard at the same inquiry.

Brennan, O'Brien and Mark Kavanagh have been charged by Racing Victoria stewards in relation to cobalt positives returned by horses trained by O'Brien and Mark Kavanagh but no dates for their hearings have been set.

Racing Victoria on Wednesday told training partners Lee and Shannon Hope that their cobalt charges will be heard by the RAD Board on October 15, two days before the Caulfield Cup.

Three horses from the Hope stable returned elevated levels of cobalt in races last year.

Leading Melbourne trainer Peter Moody has also been caught in the cobalt net but there is no hearing date for his charges.

Smith had his appeal against a 15-year disqualification for 42 cobalt-related charges dismissed by the NSW Racing Appeals Panel on Wednesday.

The tribunal has invited Smith's legal team to make submissions against the severity of the penalty.