Manchester City remain unmoved from their stance that Carlos Tevez will not be sold for a cut-price fee in January despite claims to the contrary from Corinthians and the threat of legal action by the player against Roberto Mancini for defamation.

Tevez's representatives are considering their options after the Argentina international was hit with a record four-week fine of £1m and warned as to his future conduct having been found guilty of misconduct in the Champions League defeat at Bayern Munich last month.

The Corinthians president, Andrés Sánchez, responded to the deterioration in Tevez's already poor relationship with City by telling the Brazilian media that his club's former striker will be available for less than half his summer value when the Premier League's transfer window reopens in January. A proposed move to Corinthians collapsed in July.

Sánchez said: "Although many people do not believe it, Tevez is much closer to the Corinthians than you can imagine. The initial offer was €40m and that is now €18m (£16m) because of all the problems he has faced back in England."

City are adamant this is not the case and that, given Sheikh Mansour's wealth and his belief that Tevez has shown frequent disrespect towards him and the club, the owner is prepared to hold the 27-year-old to the remaining three years of his contract – even if Mancini chooses not to select him – or until a club meets the player's market value.

Mansour and the City chairman, Khaldoon al-Mubarak, are said to be unhappy at Tevez's behaviour and the club is among the select few in the world able to withstand the pressure to sell a potentially unused £250,000-a-week asset.

They have also given their complete backing to Mancini to deploy the former Manchester United striker as and when he sees fit, although the threatened legal action against the manager could prove a major distraction to the club should the defamation case reach court.

Mancini did not discuss the situation after City's 5-2 Carling Cup fourth-round victory at Wolverhampton Wanderers on Wednesday night. A spokesperson for the club explained that was due to the legal process.

Lawyers for Tevez are assessing whether to sue Mancini over the City manager's comments that the striker refused to play at the Allianz Arena on 27 September but the Argentinian's camp will not rush to a decision on their next move. Tevez has 14 days to appeal and it seems certain he will do so, with the player expected to present his case first to City's board of directors and, should they rule against him, then to the Premier League.

City's exhaustive disciplinary hearing into the events in Munich found Tevez guilty of five breaches of contract including that he had refused Mancini's request to appear as a substitute in the 2-0 defeat. Tevez's representatives insist City's charge relates to a failure to resume warming up rather than a refusal to play.

The Premier League leaders suspect Tevez's actions may have been premeditated after he had been told six days before the Bayern game that his requests to leave the club had cost him £6m in loyalty bonuses due over the course of his contract.

They also believe his anger at being demoted to fourth-choice striker by Mancini, and confirmation that his contract would not be renegotiated following the breakdown of a transfer to Corinthians, may also have been factors.

Mancini could be successfully sued for defamation if his post-match claims that Tevez refused to play, said to both Sky and the written media in Munich, are proved false and if the Argentinian's camp can show his earning capacity has been damaged as a result of the allegation.

The trial would result in Mancini, Tevez, team-mates who were also on the bench against Bayern and the club's fitness and coaching staff being called to the high court to give evidence.

There does remain a way back for Tevez at City should he show contrition for his actions in the Champions League game and apologise to Mancini, who said the striker was "finished" with the club on the night, although that appears highly unlikely.

City could have another battle on their hands after it emerged that Kolo Touré is planning to contest any potential punishment he is given for his six-month suspension for a failed drugs test. The Ivory Coast defender, a former City captain, is due to appear before an internal disciplinary panel, chaired by City's football executive, Brian Marwood, next week, when the club could fine the player. Touré's agent, Saif Rubie, said: "Kolo is disappointed the club have decided to take this stance and he will contest any planned action against him."