Ireland manager Martin O'Neill has hit back at Paolo Di Canio with the row between the two former Sunderland managers showing little sign of abating.

The Derry man, 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 a television interview 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 £40 million 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 £10 million for.

"I think they owe a debt of gratitude to [Ireland goalkeeping coach] old Seamus McDonagh, who was out there tonight. 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, had told Sky Sports news on Friday morning: "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 £40 million to be a top 10 club and then sees the club sink into the relegation zone."

Di Canio stood by his claim that the Black Cats players were not in peak condition when he arrived on Wearside.

"The fitness levels were pathetic," he said. "I had players who told me they had cramps from driving the car.”