Pep Guardiola forcefully rejected claims made by Porto manager Sergio Conceicao that he applies undue pressure on officials.
Manchester City require a draw in Portugal to guarantee qualification as group winners and there remains animosity from the first meeting in October.
City came from behind to win that 3-1 at the Etihad on a night that left Conceicao incensed by Guardiola's alleged 'extremely unpleasant behaviour' on the touchline.
The pair repeatedly clashed, with Guardiola accused of 'speaking about our country using ugly words' during spats between the two benches.