The child, named in court only as K, was admitted to hospital with suspected sepsis or meningitis, but collapsed and died on April 6 last year. A post-mortem then revealed she had cocaine in her blood.

Her parents blamed each other for bringing drugs into the property, with the dad claiming her mum had left cocaine in a bedroom drawer. Their other four children were removed from the household.

High Court judge Mr Justice Williams has now ruled that K’s dad ‘carelessly’ brought the cocaine into the house, ‘in connection with his drug-related activities’.

He said it was probable the drug-dealer had ‘brought the cocaine onto the premises’ and ‘processed it in some way in an area which the children would have access to’.

Exactly how K came to ingest the cocaine remains unclear, the judge said. He also blamed the mother for being ‘well aware’ of the dad bringing drugs into the property, as she was also using them herself.

He went on: ‘It seems most probable that she turned a blind eye or persuaded herself that sufficient precautions were being taken to protect the children. This was to kid herself.’

The judge described K as a ‘playful, cheeky and loving little girl with all of her life to live’ and said he hoped the parents would learn from her death, The Sun reports.

He added: ‘If ever there was a lesson of the perils of drug misuse, this provides it.’

The girl had been living in London at the time of her death, and six arrests were made in connection with the case last year, a spokesperson for the Met Police said.

All were released under investigation, but an investigation led by specialist crime command is still ongoing.