The judge heading a major British inquiry into decades of child sexual abuse has said it will investigate allegations involving "people of prominence" and politicians as well as the Anglican  and Catholic churches, local councils and schools.

The British royal family may also be drawn into the probe as it considers whether "inappropriate attempts" were made by prominent figures to interfere in a case relating to a bishop.

Last month, a royal spokesperson was forced to deny that Prince Charles made an intervention in the judicial process on behalf of Peter Ball, who was jailed for sexually abusing aspiring priests - 22 years after the claims first came to light.

There have been accusations of an establishment cover-up with Mr Ball, the former Anglican bishop of Lewes and Gloucester, counting a member of the royal family among those who wrote letters of support before he was let off with a caution in 1993.

Chairwoman Justice Lowell Goddard confirmed the case will be considered by the inquiry, adding that it will "investigate whether there were inappropriate attempts by people of prominence to interfere in the criminal justice process after he was first accused of child sexual offences the case would be considered".

The New Zealand judge did not name any individuals.

The royal family has not been specifically identified as an institution being examined but it is understood it has not been excluded from potentially falling under the scope of the inquiry.

The Catholic Church in England and Wales has announced that Nuala O'Loan, the North's former Police Ombudsman, will chair a church council tasked with assisting the inquiry.

Another Irish link is the demand by Amnesty International and others that Justice Goddard should probe allegations by the late SDLP leader Gerry Fitt, of a cover-up of child abuse at the Kincora Boys Home in East Belfast.

Mr Fitt alleged the intelligence services blackmailed senior figures who got rent boys from Kincora.

But the Northern Secretary, Teresa Villers, has said the North's own ongoing child abuse inquiry should deal with Kincora.

The British government established the independent Goddard inquiry last July following revelations about late BBC presenter Jimmy Savile's abuse of hundreds of victims and a finding that 1,400 children had been abused in just one town in northern England.

It came as the £18m-a-year probe, which has been beset by delays following the resignation of two previous chairwomen, formally entered its investigative phase.

One of 12 separate strands set out by Justice Goddard was an "objective fact-finding" inquiry into allegations of abuse by "people of public prominence associated with Westminster".

She added: "The investigation will focus on high profile allegations of child sexual abuse involving current or former members of parliament, senior civil servants, government advisers, and members of the intelligence and security agencies.

"It will consider allegations of cover-up and conspiracy and will review the adequacy of law enforcement responses to these allegations."

The inquiry can compel witnesses to give evidence but is not able to determine criminal or civil liability.

There are two main categories for the investigations.

In an "institution specific" strand, failings to protect children in the care or supervision of Lambeth Council in London, Nottingham and Nottinghamshire Councils, and Rochdale Council will be examined, along with abuse in the Anglican and Roman Catholic churches.

The inquiry into Rochdale will focus in part on claims that boys were subject to sexual abuse by individuals including former MP Cyril Smith.

Custodial institutions and residential schools in both the private and state sector also face scrutiny.

The other section concerns a series of "thematic" investigations into: abuse facilitated by the internet; sexual exploitation of children by organised networks; the protection of children outside the UK; allegations linked to Westminster, and the legal remedies available to victims through the civil justice system.

Justice Goddard said the investigations will begin immediately, with all likely to lead to public hearings, with the first preliminary sessions expected to take place in February.

She said: "I am confident that this broad range of investigations will give a voice to victims and survivors who have experienced abuse in a variety of institutional settings or where there may have been institutional failings; and will combine consideration of non-recent allegations of abuse with urgent, contemporary issues of child protection."

The judge said running 12 investigations in parallel is "an organisational challenge that is unprecedented in a public inquiry in the United Kingdom", but added: "We are determined to succeed and expect the full co-operation of all institutions and individuals who can assist us in our work.

"The scale of child sexual abuse in this country requires urgent and careful attention."

The investigations are expected to take between 18 months and several years to complete. Justice Goddard said her aim of the inquiry's work being finished within five years is "achievable".