A DOUBLE killer may not have killed himself, his ex-partner and her teenage son in a huge fireball in Broadheath if experts had listened to him, a report claims.

David Potts, 39, had said he was so distressed over the break-up of his relationship with Tracy Jones, 41, that he wanted to set himself on fire and attack police officers and social workers.

The father of two - who had a history of violence, under-age sex, drunkenness and daily drug abuse - told a hospital doctor he was only unable to carry out his threat as he had no money for petrol.

But his chilling warning was ignored by psychiatrists who assessed him and he discharged himself from hospital against medical advice.

Just three weeks later Potts got drunk, armed himself with a fuel container and turned up at 4am by taxi at the family home of Miss Jones and her three children.

She and two of the youngsters who were asleep in their beds awoke to hear Potts smashing down the front door of their home on Barlow Road, Broadheath.

The terrified family dashed out onto the landing only to see him wandering up the stairs dousing the carpet with petrol as he climbed each step.

Miss Jones and her son Shaun Van Straaten, 15, tried to overpower Potts with a hammer but he flicked a cigarette lighter and engulfed them all up in flames.

As the inferno took hold neighbours pulled Tracy from the living room while Shaun staggered out himself with horrific burns.

The teenager died 48 hours later. The September 2011 blaze claimed the life of Tracy the following November. Potts himself died from his injuries on the night of the fire.

Tracey's daughter Cailin, 18, suffered severe burns but was pulled clear by a neighbour and youngest child Zach, aged four, who had been asleep in bed, was rescued by firemen also with severe burns.

Potts had been known to police, social services and mental health workers for up to 10 years and had a string of convictions for which he received non-custodial sentences.

He escaped court action over an illicit affair with a 13-year-old girl and he also once vowed to kidnap and kill one of his daughters.

He had also staged a knifepoint siege and made several suicide attempts.

Potts became 'obsessed' with blaming his bad behaviour on his self diagnosed Attention Deficit Hyperactivity Disorder which he made worse by his daily intake of two litres of cider, amphetamines and cannabis.

A report by Trafford Safeguarding Children Board said Potts' ''needs were overlooked'' and condemned Greater Manchester Police, child protection agencies and health services for 'missed opportunities' to stop him.

It said agencies failed to fully recognise the deadly potential of Potts’ 'homicidal and suicidal ideation' which arose out of his 'emotional crisis’.

Referring to Potts as ''MP'' and Miss Jones as ''MLK'', author Pamela Shelton said: ''Agencies did not give due consideration to the effects of a separation upon MP. They focused on him only to the extent that he posed a threat to MLK and her children.

''This was compounded by subsequent missed opportunities to respond to his obvious (in retrospect) high levels of distress, frustration and growing senses of injustice that was translated into threats of serious harm against himself and others.

''No-one listened carefully to him or heard what he was saying. The response by agencies to MP was insufficient. MP was desperately seeking help following his last enforced separation from MLK but no-one heard him.

''The focus stayed on MLK and her children and MP's needs were overlooked despite the research finding that the period following separation represents a more dangerous time for the victim.''

The report added: ''There was a tendency to downplay the seriousness of incidents and not complete effective risk assessments.

''MP made a specific threat to his GP about kidnapping and killing his daughter but there was an insufficient response from mental health clincians to assessing the risk of harm.

''While in hospital MP indicated intention to set fire to himself and to harm social workers and police officers. But the relatively inexperienced senior house officers who assessed him did not appear to recognise the significance of what he was saying.

''Police did not take an overview of MP and his many presentations to the force and did not view sufficiently seriously the emerging pattern of his threatening behaviour.''

Potts began dating Miss Jones in 2009 after splitting up with his wife following a stormy marriage.

But by 2011 their romance was punctuated by regular break-ups due to a deterioration in his behaviour which included an arrest for drink driving and for throwing a frying pan at his son and splashed hot oil in a girl's face.

In August 2011, a month before the tragedy, two social workers concerned about the welfare of Miss Jones and her family went round to the family home to discuss Potts and Cailin revealed he had made smutty remarks about her breasts.

As a result Tracy decided Potts was no longer welcome in her home again and he became 'frighteningly aggressive' when he turned up following the meeting - branding the social workers as 'the two bastards.'

His mother later found it difficult to calm Potts down and a probation officer concluded he was 'manipulative, controlling and aggressive’.

Locks were changed at Tracy's home and a police marker was placed on her address for an immediate response to any call for help. Officers served a warning notice on Potts accusing him of harassment over text and phone messages.

He made his arson suicide threat on August 29 to a senior house officer while being treated for a suspected heart attack in Wythenshawe Hospital. She recorded his statement in medical notes but failed to mention them to psychiatric colleagues.

In the run up to the September 19 fire, Potts left numerous messages on Facebook begging Tracy to take him back. He said much he loved her 'with all his heart' and claiming he could not understand why she didn't love him too.

Three hours before the fire he left a last posting on his Facebook page saying goodbye to friends and family and saying sorry for his behaviour.

He wrote: '''I used to be happy but now I am sad. I used to laugh but now I cry. I used to be someone, now I am no-one.''

Cailin, who was studying a BTEC National Diploma in Art and Design at Trafford College, is now living with a member of the congregation at her local church. Zach lives with his father in South Africa.

In a statement the chairman of the Trafford Safeguarding Children Board, Bob Postlethwaite, and Ch Supt Mark Roberts of Greater Manchester Police said: "Both the board and partnership acknowledge the issues identified in the report and all the agencies involved have worked hard to follow up on the recommended actions."