The letters received by NZF were complaints from a number of players, another letter followed from a previous staff member.

An independent investigator will be appointed to review the Football Ferns environment.

Football Ferns coach and NZ Football Technical Director Andreas Heraf has been given a notice of investigation with a proposal for suspension.

He is on special leave with immediate effect from both his positions.

“We are very disappointed to be in a position where some of the players from within the Football Ferns have felt the need to formally lodge a complaint with NZ Football and would like to thank them for coming forward,” said New Zealand Football President Deryck Shaw.

“We hold player welfare as a matter of utmost importance and that is why we are conducting a thorough, independent review.

"There is no place for inappropriate behaviour of any kind with New Zealand Football. 

“We are focused on creating an environment which gives the Football Ferns, and all of our national teams, the best chance of winning on the world stage,” he said.

During the press conference, New Zealand Football boss Andy Martin confirmed 13 players have refused to play for Heraf.