Martin O'Neill has hit back at Paolo Di Canio with the spat between the two former Sunderland managers showing little sign of abating.
The Ulsterman, who was replaced by the Italian following his own sacking by the Black Cats in March, described his successor as a "managerial charlatan" following a sustained attack on his regime during his stint at the Stadium of Light.
Di Canio responded in an exclusive interview with Sky Sports News on Friday, instead accusing O'Neill of being the charlatan and decrying his transfer dealings in particular.
But speaking after his side's 3-0 friendly victory over Latvia on Friday night, the new Republic of Ireland manager said: "At the end of the day, it's hardly worth it.
"You would have to go and check, but I don't think Sunderland would concur with his £40million for a start. Even Sunderland wouldn't do that.
"Seriously, one of those people he's talking about [Steven Fletcher] actually, his goals helped Sunderland stay in the league, and Mignolet, they got £10million for.
"I think they owe a debt of gratitude to [Ireland goalkeeping coach] old Seamus McDonagh, who was out there tonight, McDonagh who I think Simon Mignolet - who is playing brilliantly for Liverpool - would say he had a major influence in his career development."
Di Canio, who led Sunderland to Premier League survival last season before being sacked after five games of the current campaign, told Sky Sports News: "I don't know if he knows the meaning of this word charlatan. Probably I can teach him, even if I am not English.
"I respect the opinion of manager Martin O'Neill but the fact that he spoke after six months, not straight away, that proves what kind of level he is. He is not very big.
"A charlatan is a manager who spends £40million to be a top 10 club and then sees the club sink into the relegation zone."
Di Canio also stood by his criticism of the condition of the Sunderland players when he took over, describing their fitness levels as "pathetic".
"I had players who told me they had cramps from driving the car," he said. "I had three players with injuries in the calf after 20 minutes of a game. Six different players with problems means they were not fit."
The Italian also hit out at Phil Bardsley after the Sunderland defender claimed Di Canio tried to destroy his career.
Di Canio accused Bardsley of "treason" after he posted a tweet mocking Sunderland following their home defeat to Fulham on the opening day of the season.
"At the beginning of the season, he made tweets celebrating the defeat of the club that pay him," Di Canio added. "A person at the club came to me and said 'we want to fine him', and I agreed.
"He was celebrating, that is the worst treason for the people next to you. It is clear that he tried to destroy his career on his own."