Amir Khan has told Angel Garcia - the father of Danny Garcia - he "will beat his son" after Khan was taunted by him.
Khan and Garcia met in Los Angeles to officially announce their WBC light-welterweight title fight on 14 July.
But Garcia's father, Angel, stole the limelight by accusing the 25-year-old of being overrated.
"Danny's father does a lot of talking, but at the end of the day he's not the one who's going to be in the ring," said Khan.
"You can keep saying what you want - that I'm overrated and I'm no good - but when I beat your son, am I still going to be overrated?"
Khan's words came after Angel Garcia opened the press conference with a series of negative remarks about the former champion.
"First of all, Khan is an overrated fighter," said Garcia, who trains his son.
"There's a lot of fighters out there who are rated and we are going to execute every single one of them. We're coming out here to fight the best."
Garcia Snr also interrupted Khan during his time with the microphone, not allowing the Bolton boxer to speak at times.
Khan was due to face Lamont Peterson in a rematch after the American's controversial win last December, but the 19 May bout was cancelled after Peterson failed a drugs test.
With Khan's promoter Golden Boy attempting to have the WBA and IBF light-welterweight titles returned to their fighter, his fight with WBC title holder Garcia on 14 July at Mandalay Bay, Las Vegas, could be a unification bout.
Garcia, 24, defeated Mexican Erik Morales on points in March to capture his first world title, and Khan conceded he will be a tough opponent.
Khan said: "He's a champion; we know how good he is - he's had a good win against Erik Morales, who I'm a big fan of when he was at his peak. This is going to be a big test for me."
But Angel Garcia failed to reciprocate Khan's respect, mocking him for his defeats to Breidis Prescott and Lamont Peterson.
"First of all, Khan got knocked out in Europe. That happens, that happens to the best," he said.
"Second of all, Peterson whooped him like an octopus, hit him from all kind of angles - and then he [Khan] blamed it on the judges.
"When Danny starts hitting you with these hammers, what are you going to start to blame it on? The gloves will have rocks in them? What are you going to do? One-two, roll out, all night?"
Danny Garcia, who is currently 23-0 having beaten Morales, as well as former world champions Nate Campbell and Kendall Holt, vowed to make his record 24-0 - but also spoke of his respect for Khan.
"Khan's a great fighter; I'm a great fighter. When you put two great fighters together you get an awesome show - and that's what I'm here, that's why I signed up for boxing," said the world champion.
"You know what I bring - blood, sweat and tears. I just can't wait to show the world what I'm about. You haven't seen the best of Danny Garcia.
"I let my dad do the talking - he's the one who talks."