Alarm bells sounded by a doctor over a three-year-old boy were "ignored" by Croydon Council four months before his mother carried him into the path of a train, an inquest heard.

Social services failed to act upon a November 2012 referral from Donna Oettinger's psychiatrist, who had concerns about the impact of her mental health on her son Zaki, and closed his case without ever visiting them, South London Coroner's Court heard this afternoon.

On March 22, 2013, Miss Oettinger, 41, took Zaki to Riddlesdown station, yards from their home in Lower Barn Lane, and laid down on the rails with him in her arms. Both died instantly.

A joint inquest into their deaths heard Miss Oettinger's psychiatrist, Dr Hemanth Rao, had asked the council to assess whether her "crippling anxiety", which had grown so severe she held a knife to her neck and threatened to kill herself, was affecting Zaki's development.

In the referral to the council's Children in Need service on November 27, he added he feared Miss Oettinger could self-harm and revealed she was plagued by worries her former cocaine habit had damaged her.

Sukriti Sen, the service's head, said such a referral would usually lead to an assessment, including a home visit, within 10 days. But the council never made contact with Miss Oettinger's family.

The inquest heard a duty assessment officer - who act as a "triage" for referrals before assigning them to a relevant social worker - had not passed on Zaki's case.

Ms Sen, who investigated the failure, said: "It was never workflowed. It did not go in an inbox."

She added council's computer system had probably then automatically closed the referral.

Senior coroner Selena Lynch said: "We know effectively it was ignored. Nothing happened."

She added: "If the social worker had gone to see the family, who knows what might have happened. There are so many forks in the road."

Ms Sen told the court any assessment of Zaki, described as "bubbly and full of life" by his childminder, would have been unlikely to lead to any significant intervention.

She said: "Zaki was still going to an childminder and he was seeing professionals, such as his GP, regularly. There were no safeguarding issues. He was a happy boy."

Dr Rao said he made the referral because he was concerned about the impact of Miss Oettinger's anxiety on her relationship with son, rather than due to fears for his safety.

He admitted he should have followed up the referral when he did not hear back from Croydon Council.