NSW Waratahs coach Michael Cheika has received an official warning from SANZAR after he spoke to referee Jaco Peyper at half-time during his side's win over the Blues a fortnight ago.

A New Zealand Herald report on Thursday revealed Cheika had spoken with Peyper at half-time in the Waratahs' clash with the Blues at Allianz Stadium in a clear breach of SANZAR's code of conduct. The Waratahs had been on the end of an 8-1 first-half penalty count; a score that was reversed in the second stanza to read 9-1 in favour of the Waratahs.

SANZAR later confirmed an investigation into the incident had taken place and that no disciplinary action would be taken against either Cheika or Peyper.

"SANZAR confirms that it received a formal complaint in regard to the alleged conduct of Waratahs head coach, Michael Cheika, following the Waratahs v Blues match played at Allianz Stadium on Saturday 28 March," the statement read.

"After undertaking a thorough investigation, including receiving statements from all parties involved, it was determined that Mr Cheika had approached the match referee, Jaco Peyper, in front of the other match officials to seek clarification on a scrum interpretation during the half-time break of the Waratahs v Blues match.

"In a short and polite exchange that took place in the referee's change room, Mr Peyper responded to Mr Cheika's request for clarification. No other issues were discussed. Both Mr Cheika and Mr Peyper have subsequently acknowledged this exchange should not have taken place and apologised.

"There is no evidence that the referee was influenced by the exchange in his handling of the match, nor in the circumstances has there been a breach of the SANZAR Code of Conduct and no further action will be taken.

SANZAR has issued formal warnings to both Mr Cheika and Mr Peyper and has written to all referees and coaches, reminding them that no discussions should take place between the match officials and coaches during a match."

Waratahs chief executive Greg Harris told Fairfax Media that his franchise had already dealt with the matter but was originally unaware contact with the referee during matches was in fact a breach of conduct.

"As far as the Waratahs are concerned the issue has been dealt with and we've moved on," Harris said. "Michael was not even aware of that ruling and would not have approached the match officials' room if he had been aware of it."

The original New Zealand Herald report suggested the Blues were immediately suspicious about Peyper's change in interpretation of the laws and later learned of Cheika's visit to the official's room.

Cheika was at the centre of two separate incidents last season with the Waratahs coach first breaking a window in one of the coach's boxes at GIO Stadium in Canberra following his side's loss to the Brumbies. He was then handed a suspended sentence by a SANZAR judicial hearing after he was found guilty of abusing a cameraman.