England head coach Steve Borthwick believes World Rugby did not allow "the victim's voice to be heard" after it concluded there was "insufficient evidence" that South Africa's Bongi Mbonambi racially abused Tom Curry.
The game's global governing body announced it has closed the case unless additional evidence comes to light, meaning the Springbok hooker will start in the World Cup final against New Zealand on Saturday night.
Curry alleged to referee Ben O'Keeffe in the second quarter of the Stade de France showdown that he had been racially abused by Springboks hooker Mbonambi.
In an unexpected development, World Rugby revealed it had also been investigating an additional allegation arising from the rivals' clash at Twickenham in November 2022.
A statement said: "Having considered all the available evidence, including match footage, audio and evidence from both teams, the governing body has determined that there is insufficient evidence at this time to proceed with charges.
"It is important to note that World Rugby accepts that Tom Curry made the allegations in good faith, and that there is no suggestion that the allegation was deliberately false or malicious."
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Borthwick said: "Tom Curry has done nothing wrong. Somebody has said something to Tom Curry. Tom's reported it. Then there's been a situation that World Rugby made a decision not to allow the opportunity for the victim's voice to be heard. That's where the disappointment comes from.
"Tom's been brilliant, in terms of this week focusing on the game that we've got to play tomorrow night that we're looking forward to. And the players have been fantastic, ensuring that Tom gets all the support he needs."
The RFU said they were "deeply disappointed" by the decision made by World Rugby.
"The decision not to put the evidence before an Independent Disciplinary Panel has denied the disciplinary process the opportunity to hear Tom Curry's voice and to independently assess his account of these serious events, together with the other available evidence," an RFU statement read.
"In their continued full support of Tom, the RFU together with the England Squad, condemn the disgusting abuse he and his family has received on social media as a result of his having had the courage to put unacceptable behaviour that has no place in society or on the rugby field, in the public eye.
"Abuse of any kind is not acceptable and goes against the core values of rugby. It is important that it is safe and acceptable for everyone involved in rugby union to raise concerns, and the RFU continue to encourage everyone to report any unacceptable behaviour in the game."
SA Rugby said in statement: "Any form of racism is abhorrent to SA Rugby and the Springbok team whose purpose is to do everything in its power to assist in uniting our diverse and multicultural nation.
"Bongi Mbonambi is an experienced, respected and decorated Test player and, needless to say, denied the allegations from the outset. SA Rugby has absolute faith in the honesty and integrity of Bongi."
Springbok captain Siya Kolisi told reporters on Thursday he has reached out to Curry.
"I have spoken to him," Kolisi said. "We can take it as players when it comes to you directly, but when it's your family, it's difficult. We support each other, I feel for his family and I hope it stops."
Curry drew the incident involving hooker Mbonambi to the attention of referee O'Keeffe around the half-hour mark of the match at the Stade de France and asked what he should do in response. O'Keeffe replied: "Nothing, please. I'll be on it."
When asked after the match if Mbonambi had said something he shouldn't have done, Curry replied "yeah", although he declined to reveal what was said.
Mbonambi refused to shake Curry's hand at the end of a dramatic clash in Paris that was won by Handre Pollard's penalty after 78 minutes.
De Klerk and Pollard named in starting XV for WC final
Faf de Klerk and Handre Pollard have been named in South Africa's starting line-up for Saturday's World Cup final against New Zealand in Paris.
The return of half-backs De Klerk and Pollard are Springboks head coach Jacques Nienaber's only two changes from the side which started in last week's 16-15 semi-final win against England.
Nienaber has packed his bench with seven forwards and just one back.
South Africa: 15 Damian Willemse, 14 Kurt-Lee Arendse, 13 Jesse Kriel, 12 Damian de Allende, 11 Cheslin Kolbe, 10 Handre Pollard, 9 Faf de Klerk, 8 Duane Vermeulen, 7 Pieter-Steph du Toit, 6 Siya Kolisi (capt.), 5 Franco Mostert, 4 Eben Etzebeth, 3 Frans Malherbe, 2 Bongi Mbonambi, 1 Steven Kitshoff
Replacements: 16 Deon Fourie, 17 Ox Nche, 18 Trevor Nyakane, 19 Jean Kleyn, 20 RG Snyman, 21 Kwagga Smith, 22 Jasper Wiese, 23 Willie Le Roux.