The NRL has issued the Cronulla-Sutherland Sharks and Manly-Warringah Sea Eagles with breach notices for comments about referees following their Finals Series Week One matches.

A fine of $30,000 has been proposed for the Sharks over comments by Head Coach Shane Flanagan and other content published on the club's official website and sent to members.

The NRL has proposed a fine of $20,000 for the Sea Eagles over comments by its Head Coach Trent Barrett on Saturday night.

NRL Head of Football Brian Canavan said the penalties took into account the seriousness of the breaches, the fact that the comments went beyond acceptable parameters, and that they damaged the game during the Finals Series.

"In relation to the Sharks, there were separate breaches in the media conference following the game, in a separate interview with the coach which was sent to members and in an article published on the club's website," Mr Canavan said.

"That is why the proposed penalty is higher than we have generally issued in the past."

Mr Canavan said Manly coach Trent Barrett had already received a warning in relation to comments about match officials earlier this season.

"Our message is clear – no matter the significance of the match or the specific circumstances, coaches cannot cross the line.

"The integrity of our match officials and the game needs to be protected."

The Sharks and the Sea Eagles have five business days to respond to the breach notice.