Real Madrid's Portuguese forward Cristiano Ronaldo (R) controls the ball next to Shakhtar Donetsk's Brazilian defender Marcio Azevedo during the UEFA Champions League group A football match between Shakhtar Donetsk and Real Madrid in Lviv on November 25, 2015. AFP PHOTO / SERGEI SUPINSKY / AFP / SERGEI SUPINSKY (Photo credit should read SERGEI SUPINSKY/AFP/Getty Images)

Spanish giants Real Madrid and Atletico Madrid have been banned from registering players for the next 18-months, ruling them out of the next two transfer windows, due to breaching rules over the transfer of under-18 players.

The ban begins next month, meaning they can still sign players this transfer window, and runs until July 2017.

Atletico was also fined AUD$1.28 million and Real was fined AUD$515,000.

"FIFA works hard to protect the rights of players under the age of 18 - whether male or female, amateur or professional," said FIFA in a statement.

"This is done through the enforcement of regulations prohibiting the international transfer of minors, or the first registration of minors in a country other than their own, except in specific circumstances."