Manchester City manager Pep Guardiola hit back at Sergio Conceicao after the Porto coach's claims he pressured referees.
Conceicao accused Guardiola of pressuring referees during Porto's 3-1 Champions League loss to City in October.
Ahead of the return Group C meeting on Tuesday, Guardiola denied the claims.
"I'm not in agreement. He can say, maybe it's his opinion, but I'm not agreeing that we pressure the referees," Guardiola told a news conference.
"It's not the way that we in the history speak for ourselves. We are not the type of team to do this, honestly. I would admit it. So one thing is an action that you don't agree [with], you can make any comment, one specific action. But it's not a part of who we are, honestly.
"In the five years we are here together and the people in Germany and Spain know completely that it speaks for itself, our behaviour.
"I'm not agreeing. It's not true."
City have already secured their place in the last 16, while Porto sit second on nine points, three behind and six clear of Olympiacos.
Guardiola expects a difficult encounter, although City have won their previous three meetings with Porto by an aggregate score of 9-2.
However, City are playing an away game at Porto in European competition for just the second time and first since February 2012, when they recorded a 2-1 win in the Europa League.
"It will be tough, we know it. It’s the Champions League away. Top teams in Portugal have to win every weekend," Guardiola said.
"When you have that mentality in all departments in the club, not just the players, it makes them so dangerous. That’s why we expect a difficult a game.
"We did when they came here and it was. Tomorrow will be too."
Manchester City have had an inconsistent start to their Premier League campaign and are currently sitting 11th on the standings, six points behind leaders Tottenham but with a game in hand.
The Citizens have suffered defeats in the league to Leicester City and Tottenham, while failing to get wins against Liverpool, West Ham and Leeds United.
