The parents of two French students murdered by an offender under probation supervision began a claim yesterday for “substantial damages” against the police and Ministry of Justice.

The families are seeking compensation over systematic failures and negligence in the justice system that contributed to the deaths of their sons, Laurent Bonomo and Gabriel Ferez.

The men were tied up in their flat in New Cross, southeast London, tortured and stabbed 244 times in what prosecutors said was an “orgy of blood-letting”. Their bodies were found after an explosion sparked by the murderers set fire to the premises.

Dano Sonnex, 23, from Peckham, southeast London, and Nigel Farmer, 34, of no fixed address, were jailed for life earlier this year for the murders.

At the time of the killings in June 2008, Sonnex was under the supervision of the Probation Service after being released from serving an eight-year jail term for violence and robbery. It emerged later that a series of blunders by police, the courts, and prison and probation services meant that Sonnex was free when he should have been recalled to jail.

Anna Mazzola, solicitor for Guy Bonomo, Laurent’s father, and Françoise Villemont, mother of Gabriel Ferez, said: “This was an absolutely horrific case and Gabriel and Laurent’s family are living with the reality of it every day.

“The really awful thing for them is that the crimes could and should have been prevented. They could have been stopped if the probation service had recognised Sonnex as a serious risk earlier on. They could have been stopped if the recall process had been carried out properly.”

Ms Mazzola, of Hickman and Rose, added: “Our clients do not accept that this was just a matter of their sons being in the wrong place at the wrong time. They believe that the repeated failings of the British criminal justice system led to Gabriel and Laurent being subjected to an appalling ordeal.

“They do not believe that they have been given the answers that they need. They are therefore seeking accountability from the justice system as well as compensation in respect of the enormous damage they have suffered and the torment which Gabriel and Laurent suffered in the hours before their deaths.”

In their claim against the Metropolitan Police and the Ministry of Justice, which oversees probation services, the parents accuse them of negligence and breaching human rights law.

They claim that the Probation Service was negligent in wrongly assessing Sonnex as presenting a medium risk of harming the public and in its failure to produce a plan to manage his potential risk. The families also claim that the Metropolitan Police were negligent in failing to respond quickly to a request that Sonnex should be recalled to prison.

In their claim the families also say that the police and Ministry of Justice breached human rights laws intended to protect individuals from a risk to life.

After Sonnex and Farmer were convicted of the murders, Jack Straw, the Justice Secretary, apologised to the families for the blunders that left Sonnex on the streets when he should have been in custody for breaking the terms of his release from an earlier jail sentence. David Scott, the chief probation officer in London, resigned his post in February over the failings and expressed his “utter regret”.

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