The newsletter said City’s Fernandinho “lacked class” and referenced Bernardo Silva’s one-match ban for a tweet about team-mate Benjamin Mendy last year.
After the 0-0 draw, Porto coach Sergio Conceicao said if he had City boss Pep Guardiola’s budget and could not win then he “would be sad”.
The two managers argued on the touchline during the match in Porto.
Conceicao claimed Guardiola had used “ugly words” about Portugal.
The newsletter, which was published on Wednesday morning, followed up with a series of allegations, including that Porto were denied a clear penalty for a foul by City goalkeeper Ederson.
In addition, it said: “There should have been a red card given to Fernandinho, who despite being 35 is a clear example that football money counts a lot, but it doesn’t buy class.”
The newsletter also described Silva as being “known internationally for having been convicted of racism”.
Silva was given a one-match ban and fined £50,000 in November 2019 after a Football Association commission accepted he “did not intend” a tweet about Mendy to be “racist”.
Silva compared Mendy to the character on a packet of Conguitos – a chocolate brand available in Spain and Portugal.
City are bewildered by the newsletter but the allegation against Silva particularly annoys them given Porto were fined 20,000 euros (£18,000) by Uefa in 2012 after their supporters racially abused Yaya Toure and Mario Balotelli during a previous meeting with City.
“This is not the first time that Porto have reacted badly in circumstances like this,” said a City spokesperson.
“On this occasion it is the ill-judged and targeted criticism of some of our individual players and indeed our manager, which we wholly reject.
“In 2012, the last season we encountered them, it was the denial by the club of clear racist behaviour of their fans for which they were investigated and fined. In this context, this latest outburst is almost as surprising as it is disappointing.”
Source – BBC Sports