Racists will take "encouragement" from Uefa taking no action over abuse claims made by 17-year-old Liverpool striker Rhian Brewster, anti-discrimination campaigners say.
England Under-17 player Brewster said he was racially abused in a Uefa Youth League game against Spartak Moscow.
European football's governing body said it could find no conclusive evidence after investigating the allegations.
Kick It Out said it was "deeply disappointed" with that result.
Brewster alleged he was abused by captain Leonid Mironov in Liverpool's win over Spartak at Prenton Park in December.
Five players from each side plus the match officials were all questioned about the incident, but none could confirm hearing any discriminatory language.
Mironov admitted swearing at Brewster during the Russian club's 2-0 defeat but denied using racist language.
"The organisation is deeply disappointed with the findings of the independent investigation, with this outcome likely to give further encouragement to those who wish to be abusive in the sport," Kick It Out said.
"Kick It Out believes there are issues with clubs, such as Spartak Moscow, who have been involved in several alleged racist incidents in recent years, receiving little or no discouragement by national and international football authorities in response to allegations of racism and discrimination.
"This underlying issue is compounded with any action taken in relation to racist or discriminatory incidents rarely being appropriate. This current situation is intolerable."
Liverpool have accepted Uefa's decision and praised the "courage" of Brewster, who helped England lift the Under-17 World Cup in October.
The club added it was "very proud of the maturity, dignity and leadership Rhian has displayed in bringing focus to this issue and he will continue to receive our full support".
However the Football Association echoed Kick It Out's disappointment. "All forms of discrimination are completely unacceptable and any allegation must be fully investigated," it said.
"While we are disappointed with today's decision, we will continue to work with Uefa on how to best tackle incidents of discrimination in the future."
A Uefa statement said: "After concluding his investigation, the inspector found no evidence to corroborate the allegations, which he believed were made in good faith by Rhian Brewster.
"Therefore, the Uefa control, ethics and disciplinary body, following the recommendation of the inspector, established there was no evidence that would legally support sanctioning Leonid Mironov and thus decided to close the disciplinary proceedings."
In January, football's world governing body Fifa launched an investigation into Brewster's complaint that a team-mate was racially abused during the Under-17s World Cup in India.
Brewster - top scorer at the tournament - added in a newspaper interview that he had experienced racial abuse on the pitch since the age of 12.
He also criticised football's authorities, saying there needed to be "more severe punishments".