Australia's National Rugby League (NRL) on Thursday blocked Danny Buderus’s move to the Brumbies as their tackling coach.

Buderus had earlier been announced by the Brumbies as joining Jake White's coaching staff, but the NRL reacted swiftly and sought an explanation from Buderus's Newcastle Knights club in relation to the announcement.

"Neither Danny Buderus nor the Knights have sought permission from the NRL to enter into a third party agreement as his playing contract requires and as the club is required under the salary cap rules," acting NRL Chief Executive Shane Mattiske said in a statement.

"It is hard to envisage any circumstance where an agreement could be approved that allowed a current NRL player to promote another code competing in the same market as an NRL team.

‘‘The announcement today which saw Danny at a press conference in another code’s training gear underlines potential issues.

‘‘We will be seeking an immediate response from the Knights and as much as we respect Danny’s intentions we do not see any way in which the proposal can be pursued."

In 15 years as a league player, Buderus captained New South Wales to their last State of Origin series win over Queensland in 2005, won an NRL Grand Final with the Knights in 2001 and an English Super League title with Leeds in 2011.

He said he hopes his intended move will not spark animosity between the codes.   

‘‘First and foremost I’m a rugby league player and Newcastle Knights player. I love that club and always will,” he said.

‘‘I love the game and always will. It’s [the Brumbies job] just a consultancy role to progress in some capacity after football.

‘‘It’s not a betrayal [of rugby league], I hope it’s not out there with the Rugby League and Rugby Union thing ... I don’t think there’s too much animosity there.

The supposed deal would have seen Buderus work with the Brumbies one day per week during the pre-season and on a consultant basis once the NRL and Super Rugby seasons kick-off.

The Brumbies said they would not fight the NRL to keep Buderus if his coaching job jeopardised his playing career.