Jesse Bromwich will relinquish his position as New Zealand's captain amid allegations he and team-mate Kevin Proctor purchased cocaine following the Kiwis' Anzac Test defeat to Australia.
New Zealand Rugby League (NZRL) announced on Saturday it was investigating an alleged incident in Canberra, which emerged when Bromwich and Proctor were named in court during an appearance of local man Adrian Mark Crowther, who is accused of selling cocaine to the pair and of being in possession of four grams of MDMA.
Neither Melbourne Storm prop Bromwich or Gold Coast Titans second-row Proctor have been charged with an offence, but both released statements through their clubs on Sunday in which they apologised for their conduct.
Bromwich, who has been stood down for two games by the Storm and will undergo a counselling course, said: "I'd like to start by firstly apologising to my family, Melbourne Storm, New Zealand Rugby League, the NRL, my team-mates, the sponsors, and the members and fans.
"I regret making the choice of staying out with my team-mates until the early hours of Saturday morning, as well as consuming an excessive amount of alcohol. I take full responsibility for the poor choices I made, I am devastated and my actions were out of character.
"Playing footy for Melbourne Storm and the Kiwis is a great honour and I apologise for letting down everyone involved in both organisations.
"I will be stepping down from my leadership roles with Melbourne Storm and the Kiwis, I understand I am a role model to the young players and the poor choices I made do not reflect my personal values.
"I fully accept the sanctions that have been handed down."
Proctor added: "I have asked Graham [Annesley, the Titans CEO] to say how extremely embarrassed and sorry I am for the damage I've done to the game and my personal reputation since Friday night's Test match in Canberra.
"After the game we went back to the New Zealand team hotel and had a late dinner. After the dinner we went to a local club to have a few drinks. The rest of the night is a bit of a blur as I obviously had too much to drink before the incident that has caused all the trouble happened much later in the night.
"Although I can't remember exactly what happened, I don't deny it. I am devastated by the whole thing and can't apologise enough to my Kiwi team mates, the NRL, the Titans, and all fans of the game.
"I've never been in this sort of trouble in my career, I have never failed a drug test, and I'm so sorry I've let everyone down by losing control of my personal decisions by drinking too much alcohol. I have a wife and young family, and taking drugs is not something I support or encourage because I am very aware of the damage it can do.
"Even though I have to appear before the board later in the week, I've already decided to stand-down as club co-captain, and also stand-down from playing, until the board makes a final decision. I accept that there will be further punishment from my club and the NRL, and I just want to put this all behind me as quickly as possible and prove I can make it up to everyone."