Brazilian title chasers protest against away game ruling
"This decision adversely affects Gremio and benefits Sao Paulo," president Paulo Odone told the club's website (www.gremio.com.br).
A row over ticket prices for Sao Paulo's match added to mounting tension in the countdown to the last weekend of the 38-match campaign.
In another incident, supporters of Flamengo daubed graffiti on the walls of the club headquarters demanding the team throw their final game to help push arch-rivals Vasco da Gama into the second division.
Sao Paulo visit Goias on Sunday with a three-point lead over Gremio, who host Atletico Mineiro.
If Gremio win and Sao Paulo lose, Gremio will win the championship on games won.
Any other combination of results will hand Sao Paulo their third successive title.
Gremio were furious after Goias were handed a two-match home stadium ban for crowd trouble at a previous match and ordered to play their game in Brasilia.
Title contenders Gremio say Sao Paulo have a large fan base in Brasilia and will effectively be at home.
Goias also caused a stir by announcing they would charge an average 400 reais (£108) for tickets and, although they later reduced it to 250 reais (£68), the amount was still considered outrageously high.
"The supporters don't have this sort of money to spend on football," said Sao Paulo midfielder Hernanes, widely regarded as the top player in the championship.
"The family has to come first. With the complicated situation in Brazil I don't advise anyone to go."
Sao Paulo coach Muricy Ramalho was more concerned about suggestions his team were about to crack.
"We haven't lost for 18 games, we have the best attack in the competition and depend on ourselves to win the title," he said.
"I don't see how anyone can criticise our team."
Sunday's games will also decide the four teams to qualify for next year's South American Libertadores Cup and the two remaining sides who will join relegated Ipatinga and Portuguesa in Serie B.
Twice former champions Vasco are in the most danger.
They are 18th in the 20-team table on 40 points, two behind 16th-placed Atletico Paranaense who face Vasco's arch rivals Flamengo.
Flamengo fans painted the words "throw the game" on the walls of the club's headquarters overnight, although the graffiti was quickly removed.
The players showed their disapproval and were also upset after a group of fans demanded the resignation of coach Caio Junior, even though the team are fifth.
"The supporters should be having a barbecue and celebrating," said goalkeeper Bruno. "In any case we are professionals and we have to go on the pitch to win."