The sponsor allegedly hit by Manly forward Anthony Watmough during a boozy club function will not pursue charges, and no further action will be taken, police say.

Club sponsor Paul Durazzo said Watmough made comments about his 21-year-old daughter before punching him during Manly's season launch at a pub last Friday.

NSW police on Wednesday said the investigation into the alleged assault had concluded, with Mr Durazzo deciding not to pursue the matter.

"Police have spoken with a man alleged to have been assaulted during a function at the hotel, who has indicated he does not wish to pursue the matter," police said in a statement.

"As a consequence police will be taking no further action."

The end of the Watmough investigation is a rare piece of good news for the Manly club, which has been rocked by the sexual assault scandal involving star fullback Brett Stewart.

Stewart was on Tuesday charged over the sexual assault of a 17-year-old girl just hours after Friday's club function.

The NRL on Wednesday decided to ban Stewart from playing for four weeks, and issued the club with a $100,000 fine for its poor handling of the season launch.

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