Poppi Worthington's father will not be prosecuted over the toddler's death unless “significantly new evidence” can be found, prosecutors have announced.

An inquest found that she was sexually assaulted and stopped breathing in her father's double bed hours later but a botched police investigation has hampered criminal charges.

The coroner’s verdict was handed to the Crown Prosecution Service (CPS), but a review found there were not sufficient grounds to reverse its original decision not to prosecute Paul Worthington, who denies any wrongdoing.

Failings by Cumbria Constabulary, which lost vital evidence and failed to interview witnesses for several months, meant that there was no forensic way of proving what happened to Poppi.

The CPS said no new witnesses or evidence was presented at the inquest, where the findings are made on the balance of probability rather than “beyond reasonable doubt”, which is the bar in a criminal court.

“In order to prosecute, a reviewing lawyer would have to be satisfied that an objective, impartial and reasonable jury, properly directed and acting in accordance with the law, would be more likely than not to convict,” a spokesperson added.

An inquest found Poppi Worthington was sexually assaulted before her death (Cumbria County Council/PA)

“On each of the three previous occasions where the case was reviewed, the prosecutor decided that a jury would be unlikely to be so satisfied that Poppi had been sexually assaulted bearing in mind, primarily, the opposing medical opinion and the absence of evidence from the investigation.

“Nor that there was sufficient evidence to allow a prosecution of any other offence connected with Poppi’s death.”

Three different prosecutors have previously considered the case – first after a referral from Cumbria Constabulary in March 2015, then in June 2016 following a family court hearing and thirdly in November that year, after Poppi’s mother appealed for the decision to be reviewed.

On each occasion, the CPS decided that there was insufficient evidence to provide a “realistic prospect of conviction” for any criminal offence and said that it would only proceed if “significant new evidence” becomes available.

Fiona McGhie, a lawyer at Irwin Mitchell, said Poppi’s mother was “severely disappointed” that the inquest did not trigger a full review by the CPS.

“She was also left disappointed that Poppi’s father chose to rely on his right not to answer many questions which may incriminate him at the inquest and while she understands he was entitled to do this, she considers that the coroner’s inquiry was frustrated by this,” Ms McGhie added.

“The past five years have been a complete nightmare for her. Not knowing what happened to Poppi on that day, and knowing that there were evidence gathering failures by the police in the very early stages of the investigation has made things even worse.

“Although she is now closer to the devastating truth, it is likely that she may never get full closure on exactly what happened that night.”

An original seven minute inquest that declared the 13-month-old’s death unexplained was later quashed as “irregular” by the High Court, and the second inquest held in Kendal concluded in January.

Poppi Worthington's father, Paul Worthington, giving evidence at Kendal County Hall in Cumbria (Elizabeth Cook/PA Wire)

Mr Worthington said he put his daughter in his bed and went to get a fresh nappy at their home in Barrow-in-Furness, but reached over minutes later to find she was limp.

He rushed downstairs and Poppi’s mother, who had been sleeping on the sofa, called an ambulance.

Paramedics took her to Furness General Hospital at 6.11am but she never regained consciousness and was pronounced dead shortly after 7am.

Medics noted the child was bleeding and in January 2016, a family court judge said that in the balance of probability Mr Worthington sexually assaulted his daughter shortly before her death.

He appeared before the inquest to give evidence but used a rule meaning that inquest witnesses are not obliged to answer incriminating questions on 252 separate occasions.

Mr Worthington described his daughter as a “bully” at one hearing and would not explain how her DNA came to be on his penis, refusing to recount the hours leading up to Poppi's death.

David Roberts, HM senior coroner for Cumbria, said Mr Worthington's account did not “stand up to scrutiny”.

He ruled at some point after 2.30am on 12 December 2012, Poppi was taken from her cot and sexually assaulted although it was not the cause of her death.

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The toddler, who was suffering from an upper respiratory tract infection at the time, later died from asphyxia.

Mr Roberts told the inquest her ability to breathe was compromised by an “unsafe sleeping environment” after her father took her from her cot and placed her next to him in his double bed.

“Poppi was in such a position that her breathing was compromised, either due to the position of the bedclothes, her position within the bed or overlaying, or a combination of all three,” he concluded.

“Her viral infection would, in all probability, also have compromised her ability to breathe freely.

“In any event, when her father awoke he discovered that Poppi was no longer breathing and, shortly before 5.56am, he took her downstairs in an unresponsive state. I find that, in fact, she was dead at that point.”

In an investigation that concluded last year, the Independent Office for Police Conduct (IOPC) said Cumbria Police detectives responding to the case were “unstructured and disorganised”, highlighting the lengthy delay into a criminal investigation taking place “despite there being significant suspicious circumstances from the outset.”

Temporary Deputy Chief Constable Mark Webster said the force had liaised closely with the CPS over the past two months.

“Throughout our second investigation officers thoroughly explored every available line of enquiry,” he added.