A 17-year-old girl choked on her own vomit after swallowing a cocktail of drink and drugs, an has inquest heard.

Lorna May was found dead by friends at a flat in Newquay in March 2009 after taking methadone, diazepam and alcohol.

Social services staff in Cornwall had admitted failing the teenager who had followed her mother in sleeping rough on the streets.

Yesterday the inquest heard that following the troubled teenager's death a Serious Case Review was held into Cornwall Council's Children's Social Care.

A report by Sharon Woods, senior manager at the council's Social Work Assessment Service, admitted that more could have been done to save the girl.

She said: "The case was not open to Social Care at the time of Lorna May's death and with hindsight it is clear that there were opportunities where Children's Social Care could have provided a more robust approach and without the direction from the service other agencies were struggling with how to protect and support Lorna."

The inquest heard Lorna's parents Roderick and Lynne were divorced and in 2001 her father obtained a residency order to look after his daughter.

Lorna lived with him until 2008 when she went to live with on the streets with her mother who was homeless.

The teenager also ended up living with her grandparents from time to time, the court heard.

She was last seen alive during the early hours of March 24 and was not found until the early hours of the following day at the flat in Lewarne Road by her friends Peter Hitchens, who rented the flat, and Steve Waddingham.

While one rang the emergency services the other called three friends Hayden Lord, Karen Lightower and Kerri Billen.

Yesterday Detective Constable Jon Harcourt said efforts to trace the five to give evidence had failed because they lived rough.

According to statements read out when the inquest first opened in June, Mr Hitchens and Mr Waddingham said Lorna had drunk from a three-litre bottle of strong cider before she arrived at the flat.

DC Harcourt said methadone and heroin belonging to the two men was found at the flat but there was no evidence of foul play.

Yesterday, Karen Dale, a social work manager with the Cornwall and Isles of Scilly Local Safeguarding Children Board, said the review had discovered "confusion" in the department over how to handle homeless 16-17-year-olds.

Peter Blackwell Smith, assistant deputy coroner for Cornwall, recorded an open verdict.

He said: "We don't know what happened to Lorna and we may well never know."

Following the hearing a Cornwall Council spokeswoman said Lorna and her family had been in contact with a number of services including social care, housing, youth, youth offending and education.

According to the council Lorna's family would not give her a home because of her older boyfriend – an alcoholic and drug addict – and housing chiefs would not give them a place to live as a couple.

The Serious Case Review identified problems between social workers and housing officials in agreeing what Lorna was entitled to.

The spokeswoman said: "It also concluded that it had been difficult for Lorna to access appropriate housing from Restormel Borough Council after she left home to live on the streets with her mother.

"The council has undergone significant changes since Lorna's death.

"There have also been significant improvements in practice and service delivery with the council's Children's services.

"This includes the establishment of the single referral unit to provide greater consistency and equity to the way that referrals into social work are managed."