Castle has stepped down following two-and-a-half years at the helm of the governing body. 

This followed pressure from a group of 11 former captains of the Australian national team, comprising 1991 Rugby World Cup winner Nick Farr-Jones, George Gregan, Michael Lynagh, Simon Poidevin, Phil Kearns, Rod McCall, Jason Little, Nathan Sharpe, Stirling Mortlock, George Smith and Stephen Moore.

Earlier this week, they co-signed a letter calling on the Rugby Australia leadership to "stand aside".

"As Wallaby captains, we feel privileged to have represented our country and led our respective teams into battle, facing difficult situations together," the letter said. 

"In recent times, the Australian game has lost its way.

"It is a defeat inflicted not by COVID-19, or an on-field foe, but rather by poor administration and leadership over a number of years.

"It is with this in mind we ask the current administration to heed our call and stand aside to allow the game to be transformed, so we emerge from this pandemic with a renewed sense of unity and purpose."

Speaking to ABC, Castle revealed she had been told by the Rugby Australia Board that the organisation needed "clear air".

"I made it clear to the Board that I would stand up and take the flak and do everything possible to serve everyone's best interests," she said.

"In the last couple of hours, it has been made clear to me that the Board believes my no longer being chief executive would help give them the clear air they believe they need.

"The game is bigger than any one individual – so this evening I told the chair that I would resign from the role.

"I will do whatever is needed to ensure an orderly handover. 

"I wish the code and everyone who loves rugby nothing but the best and I would like to thank the people I work with and the broader rugby community for their enormous support."

Rugby Australia are currently in financial trouble, and last month announced a preliminary AUD$9.4 million (£4.6 million/$5.7 million/€5.2 million) loss for 2019.

It is claimed this is mainly down to the legal settlement with player Israel Folau, who launched proceedings against Rugby Australia after they terminated his contract for posting homophobic language on social media. 

Rugby Australia's situation has been worsened by the coronavirus crisis and the suspension of Super Rugby.

Castle took a 65 per cent salary pay cut, while players agreed to a 60 per cent reduction in wages.

On March 31, the governing body stood down 75 per cent of its workforce, leading to an 80 per cent overall reduction in costs across the organisation.