One of Britain’s biggest child abuse scandals is likely to have been even larger than previously thought, police revealed yesterday.

Dozens of former residents of North Wales children’s homes have given detectives ‘graphic’ accounts of appalling abuse at the hands of 84 staff – most of whom have never been prosecuted.

Barely a decade after a £13million public inquiry that was meant to uncover the extent of the scandal, police yesterday revealed they had ‘significant’ new evidence of ‘serious and systemic’ abuse.

Home Secretary Theresa May ordered the new inquiry after allegations on the BBC’s Newsnight programme last November that a public inquiry which looked at the scandal had failed to uncover the full extent of the abuse.

The now-notorious Newsnight film led to Tory grandee Lord McAlpine being wrongly implicated in the abuse.

In their first major progress report yesterday, officers who have been sifting through the accounts of former residents of the homes revealed the appalling scale of the suspected abuse.

And they warned that abusers who believed they had evaded justice should for ever be ‘looking over their shoulders’ in fear of arrest and prosecution.

The Waterhouse Report of 2000 heard from 650 witnesses and led to the conviction of seven former care workers.

The report, by former High Court Judge Sir Ronald Waterhouse, said sexual and physical abuse mainly focused on six council-run homes and two private homes between 1994 and 1990.

Yesterday, however, Detective Superintendent Ian Mulcahey, who is leading the new investigation, Operation Pallial, revealed:

– Allegations by 140 former residents, 76 of whom had not come forward before, that they had been physically and sexually abused;

– Claims that 84 people – 75 men and nine women – carried out abuse, mainly through grooming children as young as seven in their care;

– Sixteen of those have been named as an abuser by more than one person, but ten are thought to be dead;

– Abuse has been reported at 18 children’s homes across North Wales between 1963 and 1992 – more than a decade longer than uncovered by the Waterhouse Report;

– Thirty-one people are working full-time on the investigation, which has so far cost an estimated £573,000, paid by the Home Office.

The investigation is running in parallel with a review of the Waterhouse Inquiry by Mrs Justice Macur. Many ex-residents of homes including the notorious Bryn Estyn, near Wrexham, have long argued that Waterhouse’s terms of reference – focusing on abuse within the properties – meant claims of links to a wider paedophile ring in the area were ignored.

But the bombshell claim by Steve Messham to have been abused by Lord McAlpine was discredited when he was belatedly shown a photograph of the former Tory treasurer and conceded he had named the wrong man.

The furore last November led to the resignation of BBC director general George Entwistle after just 54 days in charge.

Officers working on Operation Pallial have made one arrest so far. A man was held in Ipswich last week and then bailed. More arrests are expected.

Among those who have given their accounts of being abused to the new inquiry is Keith Gregory, who was a Bryn Estyn resident from 1972-74 and is now a local councillor.

None of his alleged abusers were prosecuted, but he has given detectives the names of four he is prepared to testify against and predicted more ex-residents would now come forward.

Mr Gregory, 55, said: ‘I was worried it was going to be another whitewash after going through the Waterhouse Inquiry, so I’m very relieved.’