Australian sprint star Kyle Chalmers is confident his Chinese rival Pan Zhanle swam a drug-free race to take gold in Paris.

But that has seemingly done little to ease tensions between the pair, with Pan accusing Chalmers of giving him the cold shoulder. 

Pan had the last laugh on Wednesday night, smashing his own world record to take gold in the 100m freestyle final. 

The 19-year-old touched the wall in 46.40 seconds, 0.40s inside his previous benchmark, a time Chalmers (47.48) described as "crazy".

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But the Australian said he was confident there was no foul play involved. 

"I do everything I possibly can to win the race and trust everyone's doing the same as I am, staying true to the integrity of sport," said Chalmers, who stormed home from last at the half-way point to secure a silver medal. 

Frosty relations

China's team has been under increased scrutiny since revelations 23 swimmers tested positive to a banned substance before the Tokyo Olympics three years ago.

Pan was not in the group of 23 which was allowed to compete in Tokyo after world anti-doping authorities accepted China's explanation the swimmers had eaten contaminated food at a team hotel.

The Chinese speedster has accused Chalmers, who he has previously admitted to idolising, as ignoring him. 

“On the first day, at the 4x100 relay, after we finished swimming I greeted Chalmers. He didn’t pay me any attention at all,” Pan told China Central Television.

“Including [Jack] Alexy from the American team — when we were training and our coaches were on the sides, the movements he [Alexy] made seemed like he was deliberately splashing water on the coaches. It just felt like he looked down on us. Can I say this?”

Wednesday night's final was Chalmers's second consecutive silver in the blue riband sprinting event, having taken gold in Rio in 2016 when Pan was just 12 years old. 

Chalmers said Pan's winning time was beyond anything imaginable.

"It's a time I never dreamed or saw as possible," Chalmers said.

"The last 15 metres ... I thought I could be dead last because he was so far ahead of me."

With AAP and wires