FIFA rejected Brazil's request to allow suspended captain Thiago Silva to face Germany in the World Cup semifinals on Monday as they angrily hit back at claims referees had been ordered to take a lenient approach to foul play.

A statement from FIFA's Disciplinary Committee dismissed Brazil's plea for Silva out of hand, stating there was "no legal basis" for the defender's yellow card against Colombia to be rescinded.

In a further snub, FIFA disciplinary chiefs also ignored the growing clamour in Brazil for Colombian defender Juan Camilo Zuniga to face retrospective punishment over the aerial challenge that ended Neymar's tournament.

The statement said the committee "deeply regrets the incident and the serious consequences on Neymar's health".

But Zuniga could not be punished because the incident in Friday's stormy quarterfinal had been seen by the match officials at the time, a statement said.

Disciplinary action could only be applied retrospectively in cases of mistaken identity where a referee shows a yellow or red card to the wrong player.

The statement emphasised that even though Neymar had suffered a serious injury in the incident -- a fractured vertebrae -- it could not have a bearing on how Zuniga's case should be handled.

"We wish Neymar a prompt and complete recovery as we wish the same for all players who have sadly been ruled out of the World Cup through injury," it added.

Zuniga has apologised for the tackle and insists he had not intended to cause Neymar injury.

Silva branded Zuniga's challenge a "coward's tackle" on Monday at an eve-of-match press conference.

The Brazil captain expressed disappointment that he would not be playing after his team's unsuccessful bid to have his suspension quashed.

"My heart will be on the field. So will the heart of Neymar," Silva said.

The incident which injured Neymar in Friday's clash in Fortaleza has become the focal point of anger directed at match officials.

Several commentators have criticised the performance of Spanish referee Carlos Velasco Carballo, saying he allowed a climate of physicality to escalate, culminating in Neymar's injury, by failing to sanction players on both sides with yellow cards earlier in the game.

- Fury over leniency claim -

Carballo's performance comes after a sharp fall in the number of yellow cards issued during this year's World Cup.

The German newspaper Bild explained the drop by alleging that FIFA referees chief Massimo Busacca had told officials to limit cards in order to make the tournament more attractive.

But FIFA's chief spokesman Walter De Gregorio angrily took issue with the report on Monday, branding it as "unacceptable".

"There is a story today....that there is a secret plan from FIFA telling the referees not to sanction with yellow or red cards in order to have more entertainment or television shares," De Gregorio said.

"In other words that FIFA is risking and tolerating that players like Neymar and others are injured. This is just unacceptable."

De Gregorio did not offer any explanation for the slump in cards shown in 2014.

So far 168 yellow cards have been issued in 60 matches, an average of 2.8 per match. That contrasts with an average of 3.8 per match in 2010, and 4.8 per game in 2006.

De Gregorio said he accepted that some World Cup referees may have erred.

"This is part of the game and we accept that," he said. "But what we can't accept is the question on an ethical level, that there is a hidden plan from FIFA.

"This goes into the core business - protecting the main actors, the players, it's the most important thing we have to do at FIFA," De Gregorio said.

"We have to protect the players. If Neymar isn't playing the semi-final or the final it's not good for us too."

Tuesday's semifinal sees Brazil take on Germany in Belo Horizonte while on Wednesday Argentina play the Netherlands in Sao Paulo.