The judges' syndicate said official returns showing more than 80% support for controversial government-proposed ground rules for Egypt's first competitive presidential elections this September were rigged.
"Ninety-five per cent of polling stations were supervised by civil servants, who were intimidated by police, and were the scene of fraud," concluded the nine-page report, excerpts of which were published in the Al-Masri Al-Yom newspaper on Saturday.
The syndicate, which groups about 8000 judges, said it had been able to supervise barely 5% of Egypt's 54,530 polling stations and noted huge discrepancies in turnout between those where its representatives had been present and those where they had not.
"In the polling stations supervised by judges, turnout was low - in some cases not a single voter showed up, while in many others, turnout did not surpass 3%," the report said.
"In polling stations supervised by civil servants, turnout was in excess of 90% and even reached 100% in some cases," it said.
"This would imply that not one voter had died since the registers were last updated a year ago and that not one voter was unable to cast his ballot because he was sick, travelling or simply lazy."
The report said judges had been able to take pictures of bundles of "yes" ballots found in some boxes tied with a piece of string.
A banner on a bus in May urges
Egyptians to vote
The judges demanded that in future, voting be spread out over several weeks to allow for more supervision.
They also called for guarantees that security forces would not interfere and demanded complete control over the electoral process from the drawing up of registers to the counting of ballot papers and publication of the results.
According to official results, 82.86% of voters backed the government-proposed constitutional amendment on a turnout of 53.46%, despite opposition fury over the tough registration hurdles it set for presidential election candidates.