Worboys was found guilty of 19 charges of drugging and sexually assaulting 12 female passengers, in one case raping a woman.
He was jailed indefinitely in 2009, but the Parole Board has now decided that he would soon be released - despite police saying that more than 100 alleged victims had come forward following his conviction.
A day after his release was confirmed, the Crown Prosecution Service (CPS) defended the decision by saying it had charged Worboys with offences "where it was deemed there was a realistic prospect of conviction".
:: How the Parole Board decided to release black cab rapist John Worboys
One victim said: "I never thought Worboys would see the light of day after the terrible offences he committed. I honestly thought he would never be allowed out of prison.
"So I was shocked, shaken and tearful when a friend sent me an email with a link to the story of his imminent release.
"I hadn't been told by the Parole Board and had to find out by looking at a news website, which is completely out of order.
"I felt cheated and betrayed. They could have at least sent me a letter. "
The woman said: "I am really concerned that he could offend again. How can he carry out so many horrific crimes and then suddenly be ok?
"I feel like we need to know the reasons why the Parole Board think he is safe enough to release and whether he has admitted to any of the offences he wasn't convicted of.
"I think the police also need to investigate any other claims of women who have come forward so they too can get justice."
In a comment piece for the i newspaper, Hannah Roberts went public with a story of her narrow escape from the sexual predator.
She said police dismissed her when she told them of her ordeal in 2002. It took six years before she had the opportunity to identify Worboys and make a statement, she said.
Criticising the CPS, Ms Roberts said: "Many of the women who came forward to accuse Worboys were ignored or not believed by police at the time of their attacks.
"Now the same unheard women whose cases did not get to trial may feel slighted for a second time by suggestions that their cases did not meet the evidential test.
"The reality was that the police had accumulated a mountain of evidence that was not all needed for a successful outcome at trial and the CPS has to strike a balance between justice for victims and clogging up the courts for years."
According to the CPS, 83 women had reported allegations up to the point of conviction, and a further 19 afterwards. The CPS said it had advised officers to refer any allegations of rape.
One file was submitted in relation to an allegation of sexual assault but it "did not pass the evidential test", the CPS added in a statement.
The Metropolitan Police said there is currently no live investigation into Worboys.