Jimmy Savile sexually assaulted four children when they were aged just five – three more than police had previously said.
He abused the children between 1962 and 1976 in West Yorkshire.
The disclosure was said last night to take his offending to "a new level" but also raised serious questions over the conduct of West Yorkshire Police.
In a report on its dealings with the serial paedophile, published last week, it had suggested he had one victim of that age.
A spokesman for the force last night said the report might have been "slightly misleading", while one MP said it appeared the force's account of events was "unravelling".
West Yorkshire was already facing criticism over its report, which was written by one of its own officers, but described by one critic as "a whitewash".
It will now come under fresh scrutiny over exactly how it dealt with the investigation into Savile.
The report, written by Detective Chief Superintendent David Knopwood, stated "the youngest victim was five years old at the time of the offence", four years younger than had been recorded by a previous joint investigation by the NSPCC and Scotland Yard.
Yesterday, West Yorkshire conceded that in fact four of Savile's victims were aged five. Last night Peter Watt, the director of child protection at the NSPCC said the fact should have been in the public domain.
"I was shocked that there was one child of five that had suffered; the fact that there were four is truly appalling and I think it is a piece of information that it would have been very useful to have out in the public domain sooner, not least of which because it adds to the overall picture of what Savile was and what he was like as an abuser," he said.
"The fact that there are now a reasonable number of very young children, and boys, that clearly changes things – it somehow makes it even more shocking."
Alan Collins, a lawyer acting for 43 victims, said: "The report is pathetic. They have not been open about the number of victims aged five. It is bad enough he was abusing teenagers but now we are talking about young children which takes it to a new level."
Rob Wilson, a Tory MP critical of the police and BBC's handling of Savile and the numerous missed opportunities to catch him, said: "I said on the day that this report from West Yorkshire Police was published that I found it difficult to have much confidence in it.
"The fact that it appears to be unravelling under scrutiny suggests that there was a conflict of interest at the heart of it, between getting to the truth of its officers' relations with Savile and protecting the force's own reputation."
West Yorkshire police have already come under fire for their close relationship with the television presenter and radio disc jockey.
Eight West Yorkshire Police officers visited Savile's apartment in Roundhay – four on a regular basis.
But the report said officers had found no evidence that he was protected from arrest or prosecution as a result of his relationship with individuals in West Yorkshire.
However, it showed that 35 staff at the force only came forward with information when senior investigators demanded they do so in March – six months after the celebrity was unmasked as a predatory paedophile.
A spokesman said much of the information from the 35 officers and staff who came forward in March was "related to rumour rather than evidential material".
"None of the information would merit disciplinary action, however, the full report has been referred to the Independent Police Complaints Commission," he added.