Craig Young has resigned as St George Illawarra chairman after admitting it was an "error of judgement" to write a reference letter for Brett Finch using official club branding.
The letter written on Dragons letterhead and signed St George Illawarra chairman was addressed to the NSW District Court, where Finch is awaiting sentencing.
The NRL premiership winner has pleaded guilty to one charge of using a carriage service to transmit, publish or promote child abuse.
Finch, 41, told the court he felt "disgusted" for sending "twisted" messages about child sex abuse in an effort to obtain cocaine.
Mr Young admitted using the club's official letterhead was a mistake and said he believed stepping down was "in the best interests of the club".
"I believe this is the appropriate action, given my individual decision to provide a personal reference on official letterhead, for which I have already apologised," he said.
"I regret my error in judgement to provide the reference on letterhead, at the request of legal representatives."
Mr Young was a key part of the St George side that won premierships in 1977 and 1979, and was appointed as club chairman last November, replacing Andrew Gordon.
He said he did not regret writing the reference for his family friend.
"I do not regret my decision to provide a character reference for a long-time family friend, as to his character and behaviour prior to a damaging addiction," he said.
Mr Young was set to be replaced by WIN corporation chief executive Andrew Lancaster in November as part of a joint venture agreement.
