Claims will be made about whether detectives were warned off making inquiries into prominent figures

A three-week long investigation into allegations of child sexual abuse involving politicians and Westminster officials opens on Monday, with senior police officers, former ministers and the security services expected to give evidence.

Potentially explosive claims will be made about whether parliamentary whips’ offices withheld information about criminal offences in order to exploit it and whether detectives were warned off making inquiries into prominent public figures.

The latest strand of the independent inquiry into child sexual abuse (IICSA), chaired by Prof Alexis Jay, will examine some of the most sensitive accusations it has received. Although it will not conclude whether, for example, the former prime minister Edward Heath did or did not commit sexual abuse, it will look at the way Westminster institutions responded to such accusations.

The first week’s timetable includes evidence from the Liberal Democrat peer Dick Taverne and police officers who investigated the Elm Guest House in Barnes, south-west London, which was alleged to have been used for child grooming.

The main areas to be examined in relation to child sexual abuse include police investigations, prosecution decisions, the roles of political parties, whips’ offices in parliament, the honours system and the notorious Paedophile Information Exchange, which operated in the 1970s and 80s. One contentious issue is likely to be the extent of any public funding received by Pie.

At a preliminary hearing last year, the inquiry was told that a number of retired police officers had claimed they were indeed ‘warned off’ investigating possible cases of child sexual abuse committed by senior politicians in the 1960s, 70s and 80s.

The main aim of the inquiry will be to establish whether any Westminster institutions, political parties, government departments, law enforcement or intelligence agencies failed or are still failing to protect children from child sexual abuse.

IICSA will also inquire into whether there was a culture in Westminster institutions that shielded prominent people from investigation and tolerated wrongdoing at the expense of their victims. MI5 officials are among those due to appear as witnesses.

Allegations against the former Labour MP and peer Greville Janner QC and against the former Liberal MP Cyril Smith are being dealt with in separate strands of the inquiry, though their names are expected to surface again in the coming weeks.

It is understood that Anthony Gilberthorpe, who has previously made allegations about procuring under-age boys for Tory sex parties, has not submitted a witness statement to the inquiry and is not being called to give evidence as a witness.