Zlatan Ibrahimovic’s agent says the Paris Saint-Germain striker will sue a Swedish athletics coach who made doping allegations.

The trainer, Ulf Karlsson – who has worked with Sweden’s athletics team but never with Ibrahimovic – made the widely reported claims at a seminar, suggesting the forward had been involved in doping while playing for Juventus.

Reacting to the allegations, Ibrahimovic’s agent, Mino Raiola, said Karlsson had “made a big mistake”.

Raiola told the Swedish newspaper Expressen: “We will sue him. There are always people who hate. Maybe he is a former athlete who failed, or maybe he’s just jealous. But this man has made a big mistake. He had one life before making this statement, and he will have a different life after it. He is spreading falsehoods.

“Doping at Juventus was over when Zlatan arrived. We had plenty of doping controls there and Zlatan was tested between 15 and 20 times. Juventus were always under the microscope. The claims are just crazy – the facts are not there. All the clubs Zlatan has been at know he doesn’t even take aspirin.”

Karlsson, who said he had no evidence against Ibrahimovic, stood by the claim when approached by Expressen, saying he had been speaking at a conference discussing “how widespread doping is … And Zlatan increased weight very quickly [at Juventus]. It is unnatural to show such rapid weight gain.”

Asked how the striker had reacted to the allegation, which emerged following PSG’s Champions League draw with Chelsea, Raiola added: “I was just talking to him. He is calm. He’s more embarrassed that he missed a penalty yesterday. He said it was not his job to respond to these kinds of allegations.”

The Sweden team manager, Lars Richt, also hit out at Karlsson, adding: “I’m speechless, I have to say, that he can come up with these accusations. I don’t know what he is basing it on … the claims are extraordinary.”

• This article was amended on 7 April 2016. An earlier version said that Karlsson was a doctor