The rock star Pete Doherty will not face criminal prosecution over the death of a partygoer, Mark Blanco, in a fall from a balcony.

Relatives of Blanco, 30, were said to have reacted with fury to news from the Crown Prosecution Service that there was insufficient evidence to bring any charges over his death in 2006.

The family, which has vowed to launch private proceedings, was told by prosecutors that it could not be established that a criminal act had taken place.

Blanco, an actor friend of the comedian Jimmy Carr, was involved in a confrontation with Doherty, the star's minder Johnny Jeannevol and Paul Roundhill at a party shortly before his death, investigations showed. The three denied any wrongdoing.

The family, which claimed to have evidence that Blanco was unlawfully killed, launched a campaign after two police reports and an inquest failed to establish what triggered his fall from a balcony in Whitechapel, east London.

Jenny Hopkins, head of the CPS's complex casework, said on Thursday: "None of the evidence is capable of establishing to the required standard that Mr Blanco was thrown or pushed from the balcony or that any other individual was present at the time he fell."

Hopkins added: "As we can neither establish that a criminal act may have taken place nor identify the likely perpetrator, we must conclude there is insufficient evidence to support a charge of murder or manslaughter.

"If any further evidence does come to light, we will, of course, review our decision in accordance with our normal practices.

"We have met the family of Mr Blanco today to explain our decision to them and we would like to extend our sympathies to them on their loss."