Manly may stand down Brett Stewart and the NRL have suspended an advertising campaign featuring him following sexual assault allegations against the star fullback.

The Sea Eagles have confirmed that Stewart was arrested on Friday evening following allegations a 17-year-old girl was sexually assaulted after the club's season launch party.

The girl told police she and Stewart were chatting outside a unit block at 8pm (AEDT) in Pittwater Road at North Manly before moving their conversation into a nearby stairwell.

The girl alleges she was then sexually assaulted.

The club has denied the allegation.

NRL chief David Gallop says he has spoken to the club and they may stand Stewart down.

"Certainly, Manly are considering that over the next few days as more information comes to light," Mr Gallop told reporters in Sydney on Saturday.

"We've spoken about that being a distinct possibility.

"We've had players stood down when police charges have been laid before."

Police say Stewart refused to be interviewed and he was released without charge pending further investigations.

Making matters worse, the NRL launched their advertising campaign on Wednesday with Stewart and Melbourne five-eighth Greg Inglis as the stars of the television ad.

That campaign has been suspended in the wake of the serious allegations but the NRL said the move should not be interpreted as the league passing judgement.

Mr Gallop said the situation was "incredibly frustrating" and "disappointing".

"We have considered the matter carefully throughout the day and until further light is shed on the issue we believe it is in the best interests of all parties that the campaign is suspended for the time being," he said in a statement.

The NRL will examine alternate advertising options in the next few days.

Mr Gallop criticised players who continue to get into trouble.

"I think fans of the game are entitled to be dismayed that in these economic times well-paid footballers are, it seems, continually getting themselves in trouble in relation to abuse of alcohol."

Manly chief executive Grant Mayer declined to comment but issued a statement related to the alleged incident.

"The allegation is denied," Mr Mayer said in the statement.

"However, the club acknowledges that the investigation is ongoing and in these circumstances, and on the basis of legal advice which has been received, neither the club nor Brett will be making any further comment pending the conclusion of that investigation."

A Sea Eagles spokesman said the launch party was held at the Manly Wharf Hotel on Friday afternoon, and police had attended in response to an incident involving another player.

Second-rower Anthony Watmough allegedly slapped a sponsor, who declined to provide police with a statement into the incident.

The spokesman said the matter was settled privately on Saturday.

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