Sir Peter Fahy, the chief constable of Greater Manchester police, is to be interviewed under criminal caution as part of an investigation into whether his force allowed a teenager to enter an alleged paedophile's home as the suspect was being watched by undercover officers.

The Independent Police Complaints Commission (IPCC) announced on Tuesday that Fahy and other top officers from GMP had been placed under investigation over a series of allegations. The IPCC has launched three investigations into GMP after hearing claims from a whistleblower, who is a serving officer.

The allegations against GMP included that officers:

• bugged an office at GMP and allowed armed robbers who were under surveillance to attack a pub instead of stopping them;

• failed to intervene and detain a suspected sex offender who was under surveillance but, as police tried to gather more evidence, allowed a child to walk into the suspect's home;

• mishandled the disposal of body parts belonging to victims of the serial killer Dr Harold Shipman.

The IPCC said the investigation into Fahy related to allegations that may breach the criminal law and police discipline regulations. They stem from the allegation that GMP detectives allowed an operation into a suspected paedophile to run on too long, and thus placed a teenager in danger of being attacked. The IPCC criminal investigation into Fahy will examine how much knowledge, if any, he had about the operation targeting the alleged sex offender and the decisions it was making about when to arrest the suspect balanced against the gathering of more evidence.

The allegations from the whistleblower were first reported by the Manchester Evening News.

Tony Lloyd, police and crime commissioner for Greater Manchester, decided Fahy would not be suspended while the investigations took place. As part of the inquiry Fahy, who is vice-president of the Association of Chief Police Officers, will be interviewed under criminal caution.

In a statement, Fahy said: "As a chief constable you face making complex decisions on a daily basis about many high-risk and challenging situations. It is right that this decision-making is scrutinised and that I am held to account as part of this investigation."

Two detectives and a retired officer are being investigated by the IPCC over the allegations about the suspected paedophile.

In a statement, the IPCC said: "GMP chief constable Sir Peter Fahy has been served with a criminal and gross misconduct notice in relation to his alleged support to an allegedly poorly handled investigation into a suspected sex offender.

"A detective superintendent and a detective chief inspector were served with criminal and gross misconduct notices for their roles in the investigation. A retired officer will also be served with a criminal and gross misconduct notice over his role in the investigation."

The IPCC said GMP's assistant chief constable, Terry Sweeney, was facing an investigation for gross misconduct "for his oversight role in the disposal of body parts belonging to victims of the serial killer Harold Shipman".

The police watchdog said relatives of Shipman's victims would be kept informed of the investigation's progress. The IPCC said it had decided not to independently investigate claims that cronyism within GMP led to people being unfairly promoted. It had referred the matter back to GMP.

Fahy is currently charged in his role as chief constable of GMP over the police shooting of an unarmed man. GMP are being prosecuted for breaching health and safety laws when Anthony Grainger was shot dead in 2012. The force has pleaded not guilty.

Senior officers have faced a series of investigations in recent times. Of the top 10 forces in England, two have chiefs that are currently suspended pending investigation. They are the West Yorkshire chief, Mark Gilmore, and Avon and Somerset chief, Nick Gargan. The Metropolitan police commissioner, Sir Bernard Hogan-Howe, is under investigation for his actions in the aftermath of the Hillsborough disaster three decades ago.