Stuart Hall, the veteran BBC broadcaster, has been described as an "opportunistic predator" by the Crown Prosecution Service after he admitted to a string of historic sex offences against girls.

Three months after dismissing the allegations as "pernicious, callous, cruel and, above all, spurious", the 83-year-old was forced to admit that his accusers had been telling the truth.

Hall, of Wilmslow, Cheshire, first made the admissions at a brief hearing at Preston crown court on 16 April. But they could not be reported because he was facing trial over an allegation that he raped a 22-year-old woman in 1976. On Thursday it emerged that the rape case had been left to lie on the file, along with three other allegations of indecent assault.

Hall, wearing a dark blue suit and striped tie, stood in the well of the court as Judge Anthony Russell set him free on bail but told him he would pass sentence on 17 June.

Addressing him by his full name of James Stuart Hall, the judge said: "All sentencing options, including custody, will be available to the court. I genuinely have not made up my mind."

Hall was described as an opportunistic predator by Nazir Afzal, chief crown prosecutor for north-west England.

Outside the court he said: "We prosecuted Stuart Hall because the evidence of the victims clearly established a pattern of behaviour that was unlawful and for which no innocent explanation could be offered.

"His victims did not know each other and almost two decades separated the first and last assaults but almost all of the victims, including one who was only nine at the time of the assault, provided strikingly similar accounts. Whether in public or private, Hall would first approach under friendly pretences and then bide his time until the victim was isolated. He can only be described as an opportunistic predator."

He added: "We have this week met with the woman who alleged that she had been raped by Stuart Hall, a charge which he has denied. The welfare of complainants is a top priority for us and we always take their concerns into account. In light of the guilty pleas already entered, the complainant no longer wishes to give evidence on the allegation of rape, and we have concluded that it would not be in the public interest to take steps to make her give evidence in court. As such, we will not be proceeding with this charge.

"I would like to thank the victims for having had the bravery to come forward. This case clearly shows that the victims of abuse will not be denied justice by the passage of time and abusers will be held to account."

Earlier, Peter Wright QC, prosecuting, said Hall's 13 victims had been aged between nine and 17. They were abused between 1968 and 1986.

As he left court, Hall was mobbed by the media, but he refused to respond to questions.

In a statement issued later on his behalf, Brabners Chaffe Street said: "Stuart Hall confirms that he has pleaded guilty to 14 charges of indecent assault. Mr Hall deeply and sincerely regrets his actions. He wishes to issue an unreserved apology to the individuals concerned. He now accepts his behaviour and actions were completely wrong and he is very remorseful.

"Mr Hall also wishes to apologise to his family, friends and supportive members of the public for whom he has high regard and respect. The last five months have been a strain and an ordeal for his family, who are standing by him. He asks for privacy during the next few weeks and he emphasises that he is contrite and faces punishment with fortitude and remorse."

Crispin Aylett, defending, told the court the broadcaster's most recent offence had taken place in 1986, the first of them in 1968, "almost half a century ago".

Hall was "of otherwise exemplary character", he added, and the investigation had come "as a particularly bitter blow at this stage in his life".

Aylett said most of the offences were "one-off" incidents. "In a number of cases the parents of the complainants were aware at the time of what was said to have taken place, but they took no action apart from the perfectly sensible one of keeping their children away from the defendant."

"The defendant is, of course, sorry for what he has done. Through me he wants to apologise to his victims. He is not a man easily moved to self-pity, but he is only too aware that his disgrace is complete."

Hall, who was suspended by the BBC in December last year when the allegations first arose, was sacked by the corporation on Thursday with immediate effect.

It said: "The BBC is appalled by the disgraceful actions of Stuart Hall and we would like to express our sympathy to his victims. We will continue to work with the police to assist them in this and any other enquiries they are making."

A spokesman said: "In the light of today's events Stuart Hall will no longer be contracted by the BBC."

Asked whether any of the offences had taken place on BBC premises, the spokesman said: "The BBC has, and will continue to work with the police on all of this. We are providing the police with any assistance we can."

Lancashire police thanked Hall's victims for their bravery in reporting what had happened.

Detective Chief Inspector Neil Esseen, of the force's major investigation team, said after the hearing: "The admissions of Mr Hall will at least spare his victims the ordeal of having to recount their abuse at a trial.

"They have lived with what happened for a long period of time and it cannot have been easy for them to come forward, especially as when they did so, they did not know there were others who had also suffered abuse.

"The fact that these convictions have come a long time after they were committed shows that we will always take any allegations of sexual abuse extremely seriously and will investigate them thoroughly no matter how long ago they happened. We will always strive to protect our communities, no matter the status of the alleged perpetrator.

"I would encourage people with any information about sexual abuse or who has been a victim of sexual abuse to come forward and report their concerns confident in the knowledge it will be investigated appropriately and with sensitivity."

Hall's eccentric delivery had made him a popular figure in British broadcasting for half a century. He was awarded an OBE in the New Year honours list of 2012.

The allegations against him emerged in January, and the father of two was subsequently charged with three separate indecent assaults of young girls between 1974 and 1984. He then faced the rape charge and 14 further charges of sexual assault against 10 girls between 1967 and 1986.

Hall used the occasion of his first appearance at Preston crown court to make an emotional plea of innocence – and to question why the allegations had taken so long to surface. Standing beside his then lawyer, the one-time It's A Knockout presenter said: "The last two months of my life have been a living nightmare. I have never gone through so much stress in my life and I am finding it difficult to sustain."

He complained of a heart problem and said he would be "very lucky to survive another couple of years". Hall went on to say he hoped he survived those two years so he could "regain my honour and reputation and, more than ever, my life".

"Fortunately I have a very loving family and they are very supportive. I think but for their love I might have been constrained to take my own life. They have encouraged me to fight on, to fight the charges and regain my reputation and good name and whatever I have represented to this country down the years."

Hall's then lawyer, Louise Straw, had previously described him as the victim of a "clear pursuit of celebrity".

The broadcaster is married to Hazel, 74, and the couple have two children, Francesca, 52, and Daniel, 50.