Victims of the football coach Bob Higgins, who is beginning a 24-year jail term for abusing schoolboy players, have said there are still many questions to be answered about why he was able to evade justice for three decades.

Survivors called on high-profile players and managers who worked with Higgins at Southampton FC to explain what they knew of his offending and claimed that by remaining quiet they continued to protect him.

They said Peterborough FC, where Higgins was also employed, and the Football Association also needed to come clean about why he had been able to coach and abuse youth players for seven years after concerns were raised about him.

Higgins, 66, from Southampton, showed no emotion as Judge Peter Crabtree jailed him at Winchester crown court for the abuse of 24 schoolboys over a 25-year period from 1971 to 1996.

The judge said Higgins was a cunning and manipulative predator who abused his position of trust as a respected coach and caused real, enduring harm to his victims. Higgins had not shown a jot of remorse, he said.

Many of his victims, now middle-aged men, sat in the public gallery as Higgins was sentenced. They had testified to suffering decades of mental health problems because of his crimes, and expressed anger, shame and guilt at what had happened to them.

Some told the court they had tried to kill themselves, and many said they had struggled over the years with flashbacks, panic attacks, depression, anxiety, lack of trust and problems with personal relationships. A number went on to have good careers in football, but some said they had lost their chance of fulfilling their potential because of Higgins.

After the sentencing, Hampshire police said more people had come forward to make allegations against Higgins since his conviction and that the possibility of further prosecutions had not been ruled out.

On the steps of the court, survivors made it clear their fight for justice was not over. The former Southampton youth player Dean Radford described how he and other boys came forward in 1989 to reveal that Higgins had abused him but were not believed.

“We hope those Southampton club directors, high-profile players and management who spent time with Higgins will stand up and tell the truth,” he said. “We believe many people must have known what was going on. By not speaking out these people were and still are protecting a predatory paedophile.”

Radford paid tribute to the former Southampton junior star and Higgins victim Billy Seymour, who died in a car crash earlier this year. He said: “Billy will be looking down on us smiling knowing Bob Higgins cannot harm any other child ever again. He will never be forgotten. We did it Billy, just like you said we would. You can now rest in peace our dear friend.”

Higgins worked with youngsters at Southampton between 1975 and 1990 and at Peterborough between 1994 and 1996. When the Guardian broke the story of abuse within football in 2016, Higgins was still working in the game, though not as a coach of junior players.

Dion Raitt, who was abused by Higgins as a junior player at Peterborough, said Higgins used the boys’ hunger to succeed to exploit them. He said: “Football was our lives, football was our dreams. We would have done anything to make it as a professional footballer.

“There remain many questions that we deserve answers to. How was Bob Higgins able to slip through the net for so long? How was he ever put into a position of power at a professional football club like Peterborough United?”

Raitt said it was “especially shocking” that in 1989 the Football League, then the game’s governing body, had issued a warning to all clubs about Higgins. “Sadly because of potential failings we were subjected to horrific abuse at the hands of Higgins,” he said.

During the sentencing hearing, another victim, who cannot be named, criticised the FA and Southampton over their handling of Higgins. He asked the court: “Where were Southampton? Where were the FA? Where was their due diligence and safeguarding policies? They had a duty of care, a responsibility.”

Two other former Southampton youth players, Anthony Connolly and Lee Smith, waived their right to anonymity. Connolly had told the court he first met Higgins when he was 12 and said the coach groomed his parents as well as him. Addressing Higgins directly, he said: “You took away my childhood.”

He said the abuse created a “void inside of me” filled with “fear, anxiety and torment”. He said he had turned to drink to try to drive the fear away and suffered mental health issues. “I hope Southampton FC and the English FA have learned from their mistakes,” he said in court. “I hope the proper safeguarding is in place.”

Smith described Higgins as a monster who ruined the dreams of his victims for his own “sick perverted satisfaction” and said: “The football community is now a much safer place.”

Southampton and Peterborough have apologised to the victims. After Higgins’s conviction the FA said it recognised their distress. “We continue to signpost victims and survivors to speak to Clive Sheldon QC whose team is conducting the independent inquiry into allegations of non-recent child sexual abuse in football,” it said

Both football clubs declined to comment on Wednesday on the former players’ calls for more answers.

An FA spokesperson said: “The FA has commissioned an independent QC to conduct a review into, what, if anything, the FA and clubs knew about the allegations of child sexual abuse at the relevant time, and what action was taken or should have taken place.

“It is therefore inappropriate for the FA to comment on these questions whilst that review is ongoing.”