Joel Monaghan has broken down at a press conference in Canberra after explaining his decision to quit the NRL over a photo "prank which has caused so much pain".

Monaghan was facing the sack after a photo of him in a lewd pose with a dog was circulated on Twitter last week.

He chose, however, to fall on his sword before the Raiders board could sack him.

A tearful Monaghan said he was leaving for the sake of the team.

"I'll have to handle the jokes and taunts, which is understandable, but the players shouldn't have to put up with the pressure that my ongoing presence will bring," he said.

"I've received a huge amount of support from all the players and loved ones, but the reality is that a prank isn't going to be forgot anytime soon.

"I've phoned all major sponsors of the club today and apologised for my actions."

During the emotional apology, Monaghan confirmed he was looking to continue his career in the English Super League - where his brother Michael plays for Warrington.

"They were my actions and I'm solely responsible for the prank which has caused so much pain," he said.

"Alcohol is no excuse.

"I'd like to thank my team-mates, coaching staff and loyal fans."

After trying a few times to continue his statement - once saying "this is torture" - Monaghan broke down in tears and retreated indoors.

Raiders chief executive Don Furner stepped forward to front the media.

"Joel is welcome back at this club and I hope he does come back one day," Furner said.

"I hope he is welcome back in Canberra because he has done a lot of good in this city.

"He's had to pay a very high price for a silly party prank at a private house."

Furner added the club had no idea how the photo was leaked.

"I can assure everybody here that we don't know who took the photo, if it was one of our players," Furner said.

"There's no way in the world that they would want this to happen to Joel, there's no way in the world that one of our players would have uploaded this onto a website and wanted this to happen to Joel."

Monaghan had two years left on his Canberra contract and the Raiders board agreed to an early release.

He met his manager Jim Banaghan last night and again this morning.

Monaghan singled out team-mate Terry Campese for special thanks for sticking by him through the ordeal and for pleading with the club to keep the representative winger in Canberra.