London police said this afternoon they had ended a high-profile inquiry into allegations that politicians and senior public figures were part of a paedophile ring that had murdered three young boys and no one would face criminal charges.

The investigation was launched in late 2014 after an alleged victim, known only as Nick, told detectives he was sexually abused at locations including military establishments and at Dolphin Square, a central London block of flats close to parliament.

Police initially described the allegations, dating back to the 1970s and 80s, as "credible and true", a statement detectives later acknowledged was misleading.

A number of prominent figures were among the suspects, including the late former prime minister Edward Heath and late ex-Home Secretary Leon Brittan.

The force said it would not apologise for carrying out its duty

However, police said the investigation, which involved 31 officers, had not found any evidence that justified prosecutions and that the much-criticised inquiry, known as Operation Midland, would be closed.

The force said it would not apologise for "carrying out its duty".

"It is absolutely right that we assessed carefully the allegations made to us in October 2014 and did not dismiss them prematurely," Deputy Assistant Commissioner Steve Rodhouse, the officer in charge, said.

"Our initial inquiries supported the need for a thorough investigation to seek any evidence that might corroborate or disprove the allegations."

Operation Midland has been condemned by those identified as suspects, and London's police chief Bernard Hogan-Howe has faced pressure from the media to apologise to those involved.

In a statement, former lawmaker Harvey Proctor, who was told on Monday he would face no further action, said the man who made the allegations should be prosecuted for trying to pervert the course of justice and that Hogan-Howe and other senior officers should resign.

Over the past few years, Britain has been rocked by a series of child sex scandals and revelations that celebrities and politicians were involved in widespread abuse and police had failed to act when suspicions were raised.

A New Zealand High Court judge is now overseeing a major inquiry into decades of child abuse and whether powerful figures covered it up.

However, critics and well-known figures who have been arrested but later cleared of wrongdoing have said many of those accused are victims of a witch hunt, unfounded rumours or the claims of fantasists.