Gremio president Romildo Bolzan says Barcelona have not made an offer for midfielder Arthur, who appeared in leaked images recently wearing the Catalan club's shirt.
Barca's sporting director Robert Fernandez travelled to Brazil last month to watch Arthur produce a man of the match performance as Gremio won the Copa Libertadores for the first time since 1995.
Robert, along with Andre Cury, Barca's representative in South America, was then photographed with Arthur, who was wearing the La Liga club's latest home shirt.
Speaking to Marca ahead of Gremio's Club World Cup final against Real Madrid on Saturday, Bolzan claimed Arthur was "inadvertently" put in an awkward position and told any club wanting the 21-year-old that they will have to pay €50 million.
"I was surprised by the photograph in the Barcelona shirt," he said. "The club knew there was a lunch with a Barcelona director, but we didn't know who it was.
"It was a strange situation -- a careless one that [Arthur] was put in inadvertently. It annoyed us a lot, but it's in the past now."
Asked if, as some reports suggested at the time, Gremio would report Barca to FIFA, he added: "No. For now, we're going to see how the situation evolves. Everything that passed was in private and we're going to leave it there for now."
Diario Sport reported on Friday that Barca will send a delegation to Brazil next week to tie up deals for Arthur and Palmeiras defender Yerry Mina.
But Bolzan, who is currently in the United Arab Emirates at the Club World Cup, says there has been no contact from Barcelona yet.
"There's no offer from Barca," he said. "None. They've not been in touch with us and if they do we will tell them the only way Arthur leaves is if they pay the buyout clause: €50m."
Barca may face competition for Arthur's signature, too, with Chelsea and, more recently, Real Madrid reported to be keen on the Brazilian.
"At the moment, we're pointing to his release clause and I don't think our posture will change," Bolzan said when asked if he would be more open to interest from Barca's rivals Madrid.
"We're talking about a 21-year-old player who has been in the Brazil squad and we believe he will be at the World Cup, too. He's been the revelation of the season in the Brazilian league and has a fantastic future."
Arthur has previously confirmed he has held talks with Barca but says nothing has been finalised.