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The American raised doubts about Sullivan's rapid improvement to shave 0.08 seconds off Russian Olympic champion Alexander Popov's 2000 mark in a new record of 21.56 seconds in Sydney last month.
Hall, who is aiming to win a third straight Olympic 50m freestyle title in Beijing later this year, compared Sullivan's performance to that of drug cheats and says the public has every right to be suspicious of his swim.
"I am not accusing Eamon of cheating," Hall told Australian Associated Press by email Friday.
"I have been in this sport for a very long time and I have never seen such a drop in time from an elite level swimmer.
"Similar drops have been made by athletes that later were proven cheaters.
"It's no fault of Eamon that a lot of people are going to look at his swim suspiciously, unless, of course, he did cheat.
"Too many athletes have cheated. The public has a right to be suspicious of doping when they see a drop like that."
Hall said he was surprised Sullivan had lowered his best time from 22.00 seconds to 21.56s in a single swim without being fully tapered.
Hall's claims were dismissed by Sullivan's coach Grant Stoelwinder, who said the 22-year-old Australian had improved his times through maturity, uninterrupted training and extensive worldwide racing.
"I don't to feel like we have to justify (Eamon's) time," Stoelwinder said.
"He was blood and urine tested after the world record swim and also this week."
"This is a pity about elite sports these days. When somebody does something special that is the first thing that somebody wants to say."
Source : Agency.