Rangers' Glen Kamara insists he was racially abused by Ondrej Kudela and said the Slavia Prague player's denial is "a complete utter lie".
The Finland international was visibly distressed at a comment made late in the 2-0 Europa League loss at Ibrox.
Kamara said: "I was shocked and horrified to hear such racist abuse from a professional football player."
In a statement via his lawyer, Kamara claims Kudela covered his mouth, swore and used a racially offensive term.
Because of their offensive nature, the BBC are not reproducing the words.
Kudela admitted swearing while covering his mouth but not the "disgusting accusation" of racism.
Kamara added: "As a player I do not expect myself, nor any other to have to tolerate racial hatred on or off the pitch in 2021.
- Slavia to file 'brutal attack' complaint with police
- Goldson fumes at 'token gestures' on racism
- Rangers demand racism response from Uefa
"The vile racist abuse by Ondrej Kudela took place on the international stage and any failure to act by Uefa will be viewed as a green light for racism.
"There is no place for racism or any form of bigotry in football. Since the summer many of us have taken the knee in solidarity with those who have lost their lives to racial violence.
"If Uefa genuinely wants to 'show racism the red card', then it's time to stop the tokenism and take a zero-tolerance approach."
Slavia Prague complained that Kudela was the victim of a "brutal attack" after the game and have said they are progressing with a criminal complaint.
As for Kudela's version of events on the pitch, Kamara described that as "a complete utter lie, which does not stand up to any form of scrutiny", adding that it was loud enough for team-mate Bongani Zungu to overhear.
"I am grateful for the unconditional support of my team, our club and especially our manager Steven Gerrard," Kamara added.
"I want to thank not just our Rangers fans, but the many fans from across the football community and beyond, for calling out racism not just against myself, but also fellow player Kemar Roofe, who was subjected to a tirade of racist bile on Instagram.
"We as black players are sick of the freedom that such bigots are given to parade their hatred on social media and wonder when the likes of Instagram will start to take action."
Slavia say their criminal complaint details a list of witnesses, including Rangers manager Gerrard.
A statement explained that the Czech Embassy in London will officially file the club's grievance but a Police Scotland spokesperson said on Friday: "No reports of criminality have been made by either club in connection with last night's match.
"Police Scotland has contacted club officials and assured them that should any allegation be received it will be investigated thoroughly."
Slavia assert that the alleged post-match assault on Kudela was "thought out, including deliberately covering the cameras at the scene of the incident", adding that the "brutal attack was carried out with full intensity in order to injure and cause physical damage".
They say delegates of European governing body Uefa and members of their own staff witnessed the incident, along with Gerrard.
Furthermore, Slavia have said they will also make a criminal complaint and start and investigation after a image appeared of fans of the club holding a racist banner referencing Kamara.
Rangers managing director Stewart Robertson said his club expect a "robust and unequivocal response" on the matter from Uefa.
Uefa has already confirmed it will conduct an investigation into the events at Ibrox.