French club Clermont were "responsible" for the harm former player Jamie Cudmore suffered after sustaining a concussion, a neurologist has told a court.

Cudmore, 40, left the pitch during the 2015 Champions Cup final but returned after an assessment by Clermont's doctor.

"The damage suffered by the claimant who sustained a head injury in the 56th minute of the game played on May 2 2015 is the responsibility of ASM (the club)" the expert medical witness Francois Chedru wrote in his report to Clermont's regional court on Thursday and seen by AFP on Monday.

Chedru said Cudmore was not fit to return to the field of play.

The law firm representing Cudmore said the outfit where the Canadian spent 11 seasons had attempted to disparage his case. 

"ASM behaved in an irresponsible way in relation to Mr. Cudmore. They haven't stopped in their defense with the advice from Professor Chazal which has been made public by club president Mr. Eric de Cromieres to try and discredit the legitimacy of Mr. Cudmore's procedure by going as far as denying the existence of the concussions," the firm Portejoie said in a press release.

Clermont's lawyer denied any liability. 

"No responsibility of the club's doctor can be looked for because an expert has clearly recognized a lack of a link in blame between the error committed by the club's doctor and the small damage suffered by Mr. Cudmore," the club's lawyer said. 

Cudmore was one of Canada's most uncompromising players. His brother is also well-known; Daniel Cudmore played Colossus in the X-Men movies, and was also a rugby player in his youth.  

Jamie Cudmore began the original case in 2017, accusing Clermont of playing with his health after they forced him to stay on the field two weeks earlier after also suffering a head injury during the preceding semi-final in Saint-Etienne.

Cudmore's legal representatives claimed the risks taken could have had dramatic consequences on his health. 

The two-time French champions are the first club to be accused of such actions.

The claims come after Racing 92's South Africa international Pat Lambie, 28, announced his retirement from the sport on Saturday due to effects of suffering three concussions in the space of one year and a half.

Lambie said he had hidden the symptoms during this year's Champions Cup semi-final as he was worried he would have to miss the final which was taking place a fortnight later.

These two incidents have followed a serious injury to Clermont's Samuel Ezeala which led to French rugby's medical observatory to recommend 45 measures to protect players.

One idea which has been adopted is to increase the number of substitutions possible during a game from eight to 12 in the two top tiers of the game in France.

These actions have been overshadowed with the rugby-related deaths of two academy players in Louis Fajfrowski and Nicolas Chauvin as well as two amateur youngsters in recent months.

World Rugby and the French Rugby Federation have scheduled a forum on injury prevention in Paris on March 19-20.

© Agence France-Presse