An inquiry into allegations of child sex abuse linked to Westminster is looking at “extremely serious issues” and aims to address “outstanding questions of public concern”, its opening day has heard.

The latest strand of the wide-ranging Independent Inquiry into Child Sexual Abuse (IICSA) faced criticism before its main hearing took place on Monday, being branded a “witch hunt against dead politicians”.

Acknowledging that the inquiry’s work has its critics, lead counsel Brian Altman QC argued that there remains a public appetite for investigation into such issues.

The Westminster strand is one of 13 being considered by the inquiry, which was set up in 2015 in the wake of the Savile scandal and amid allegations that a paedophile ring once operated in Westminster.

Mr Altman told the London hearing the inquiry will not consider allegations made by Carl Beech, who had been known as “Nick”, claiming there was a Westminster paedophile ring operating in Dolphin Square.

Beech has since been charged with perverting the course of justice and fraud.

But he said there are wider “issues of public concern” that remain outstanding.

Mr Altman said: “It is our firm submission that public concern over Westminster child sexual abuse allegations neither begins nor ends with Mr Beech.

“We suggest, and we are confident that many of the core participants here today will agree, that there are outstanding questions of public concern in this area that it is both necessary and appropriate for this inquiry to investigate, albeit in a limited and proportionate manner.”

He said a question raised by Labour’s Tom Watson in the House of Commons in 2012, saying there was ​“clear intelligence suggesting a powerful paedophile network linked to Parliament and No 10″, could be seen as the “catalyst for the establishment of this inquiry”.

Mr Altman added: “Unsurprisingly, Mr Watson’s question gave rise to considerable public concern.”

Representatives of MI5, the Metropolitan Police and the Independent Office for Police Conduct will also be called as witnesses during this month’s hearings.

The probe will look into whether political parties turned a blind eye to allegations and if there were attempts to cover up abuse claims.

Three case studies will be considered, including how the Liberal Party, now the Liberal Democrat Party, responded to allegations made against the late MP Cyril Smith, how the Conservative Party and other Westminster institutions dealt with allegations against the late Conservative MP for Chester Peter Morrison.

A more recent case study will look at Green Party member David Challenor, who, the inquiry heard, was jailed for 22 years last year after being convicted of sexual assault against a 10-year-old girl.

He had been allowed to remain an active member of the party while he awaited trial, Mr Altman told the hearing.

The operation of the Whips’ offices in Parliament and the existence of so-called “dirt books” containing “scandal” about MPs, will be examined.

Another area of interest is the honours system, following concerns around honours potentially being granted to people accused of abuse either before or after their nominations.

The inquiry will also look at claims around the funding of the Paedophile Information Exchange, while the final topic concerns current and future safeguarding and child protection policies in parties, Government and the intelligence and security agencies”.

The IICSA has stressed that allegations against people accused of wrongdoing during the hearing are not necessarily true.

Daniel Janner QC, son of the late Labour peer Lord Janner, speaking outside the inquiry before Monday’s hearing began, claimed allegations forming part of the probe are based on “tittle tattle, false rumours and dodgy dossiers”.

Daniel Janner QC speaks during a press conference outside the IICSA hearing building in London
Daniel Janner QC speaks during a press conference outside the IICSA hearing building in London (Dominic Lipinski/PA)

He said: “This beleaguered inquiry behind me has turned into a witch hunt against dead politicians, such as Sir Edward Heath, Lord Brittan and my late father, Lord Janner.

“It will unjustly trash their reputations.

“They cannot answer back from the grave.”

Allegations involving Lord Janner will be dealt with in a separate strand of the inquiry.

The hearing continues.