Sexual abuse was rampant at a children's home in Northern Ireland run by a Catholic order of brothers, a senior police officer has said.

Around a fifth of boys at Rubane House in Co Down were subjected to sexual or physical abuse, according to a public inquiry, equal to if not worse than that by loyalists at another home, Kincora in east Belfast.

Rubane was the subject of a police investigation in 1995, the Historical Institutional Abuse inquiry was told. Three De La Salle order brothers were charged but none convicted after their trials did not go ahead due to legal issues.

Former Royal Ulster Constabulary (RUC) detective chief superintendent Eric Anderson wrote a note to the Director of Public Prosecutions.

It said: "Sexual abuse by a considerable number of the De La Salle brothers on the children and consequently between children is rampant."

It said most of the offenders were dead or medically certified unfit for trial.

"The full horror of the abuse in this establishment is reflected in 41 files already submitted through your office to the DPP.

"I consider the complaints made to show it to be on a par with, if not worse than the abuse at the Kincora children's home (a notorious establishment frequented by loyalists in East Belfast)."

Between 1951 and 1985 around 1,000 children stayed at Rubane, near Kircubbin on the Ards Peninsula. Abuse of around a fifth of residents ranged from watching boys in the showers for sexual gratification to rape as well as physical attacks, lawyer for the public inquiry Joseph Aiken said.

Alleged victims of notorious paedophile Fr Brendan Smyth, who was associated with Rubane, are expected to give evidence to the inquiry.

Mr Aiken said abuse dated back to the 1950s and extended far more widely than Fr Smyth. In the 1950s the person in overall charge at Rubane, now dead, embarked on a 20-year litany of attacks, he said, adding that the abuse was similar in its gravity to Fr Smyth's.

"The oral evidence over the coming weeks will continue to be extremely harrowing and difficult to hear, however individuals have come forward to the inquiry with the desire, however difficult it may be for them, and want the opportunity to publicly explain what happened to them when they were supposed to have been in the care of the (Catholic) Diocese of Down and Connor and the De La Salle order."

The inquiry was set up by Northern Ireland's power-sharing administration at Stormont.

It is chaired by former High Court judge Sir Anthony Hart.

Its remit is to investigate what took place at 13 residential children's homes run by religious orders, voluntary organisations and the state in the 73-year period up to 1995.