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," he 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."
Preparing for Portugal!November 30, 2020
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."