Substitute back-row forward Damien Chouly later scored a try, with Camille Lopez's 100th-minute conversion giving France a dramatic 20-18 victory.

Slimani had earlier been replaced, but the France team doctor insisted that Atonio needed an HIA, therefore allowing Slimani to go back on as France laid siege to Wales' line through a series of scrums.

And Wales also left Stade de France amid suggestions that wing George North was bitten during the frenzied finale.

"Integrity in our game is pretty important," Wales' interim head coach Howley said.

"What happened towards the last 10 minutes shouldn't happen again on an international rugby field.

"The process leading up to the change of the French tighthead, the way that process occurred, we love our game too much to have those decisions. It was hugely disappointing.

"The process - him (Slimani) warming up prior to him going back on. One of their coaches outside the technical area had a conversation with the doctor, and within a minute of it, the tighthead was taken off.

"In terms of the HIA and the process, I've spoken to Wayne (match referee Wayne Barnes) to talk about that process. The evidence suggests that it is not in the integrity of our game.

"There is a technical area, and you are not allowed outside that. Ultimately, someone has come outside that and allowed the doctor to go on at a break in play, which is outside the laws of the game.

"You can hear Wayne Barnes ask him (Atonio) if he is okay. He (Atonio) said he had a sore back, but that he was okay. And then the doctor comes on, and he goes off.

"Wayne, in terms of the last 10 minutes, that wasn't Wayne's fault. He has listened to a medic.

"You can imagine the emotional fall-out. I don't know what can be done, because ultimately it is the trust of the information between management and a referee.

"Whoever has come outside the technical area - I don't know who it was - but he has been able to get to someone to get on the field, and they were able to make that switch.

"The integrity of the game has been brought into disrepute."

Asked by a journalist during Wales' post-match press conference if he would call it cheating, Howley added: "I just question the integrity of our game, and the decision that was made.

"If you want to call it that, that's entirely up to you. We love our game, which is why we are involved in it. What we witnessed in the last 10 minutes, I haven't seen that before in the international game.

"I have spoken to Jon Davis of the Six Nations committee, and I've been in to see Wayne several times. We will look through the whole footage."

Howley's opposite number Guy Noves, when asked about the prop change, said: "They told me he (Atonio) was injured, so I have to take my responsibility.

"We will do a medical check-up. I hope the injury is not too serious, and he will be able to play again soon."

The fall-out from an alleged bite to North, meanwhile, could be considerable. Barnes and his fellow officials asked for video footage, but it proved inconclusive and no action was taken.

Howley added: "It's gone to the TMO (television match official). The evidence was inconclusive in terms of the images that were shown to the referees, and ultimately they've made a decision on that and it's absolutely fine.

"I am 100 per cent behind that decision in terms of the pictures they saw. Obviously, there is evidence to suggest otherwise on George's arm.

"The evidence suggests there is a bite.

"The referee only had one angle. I haven't seen any other angles, so unfortunately it's inconclusive and you move on.

"I am sure you can ask George if you can have a look at his arm. There is evidence to suggest that there is a bite."

When the biting allegation was put to Noves, he said: "I am sorry, I haven't seen, so I don't know."

Wales led 18-13 thanks to six Leigh Halfpenny penalties heading into stoppage time, but replacement prop Samson Lee was sin-binned before Wales almost held out for what would have been their sixth successive victory over France.

"Ultimately, we defended for our lives," Howley said.

"The team was outstanding - their desire, their fortitude - it was backs against the wall stuff.

"We didn't start too well. Whe you come to Paris, you have to start well. But we weathered the initial storm and got back into the game."

Centre Remi Lamerat scored an early try, while Lopez finished with two conversions and two penalties as France ended their Six Nations campaign on a winning note.

Noves said: "I am very proud of the players, and I think the public loved it. The French team has shown what it can do this season.

"Many matches can be a benchmark. It is too early to say what was good and bad for us in the tournament.

"We have to remain clear-headed. The players have learnt that if you keep the ball, you will score the try."