The specialist psychiatry service which failed to offer help to a mother before she killed her baby daughter still suffers from weaknesses identified six years ago by a NHS whistleblower, it is claimed.

Support could not be offered to Erin Sutherland by NHS Lothian's perinatal service when her daughter Chloe was eight months old, two months before the mother smothered her on February 3.

An inquiry is being launched by Scotland's mental health watchdog after Sutherland, 36, of Edinburgh, pleaded guilty to culpable homocide at the city's High Court on Tuesday.

The perinatal unit is based at the mother and baby unit (MBU) at St John's Hospital in Livingston. Sutherland's family doctor had contacted a perinatal mental health team for her to see a community psychiatric nurse (CPN) following a consultation in December last year.

The Herald revealed last year Dr Hamilton had made allegations of harassment, bullying and victimisation after she "blew the whistle" over the safety of the perinatal service.

The established consultant, who specialises in perinatal psychiatry, has since left NHS Lothian. But she challenged the suggestion made in court that post-natal depression was not deemed to be a problem after six months.

Dr Hamilton said: "I would say that any competent specialist perinatal psychiatrist would, without doubt, regard serious post-natal depression as a problem that could arise any time up to at least one year post natally, and that having a previous history of serious problems (as Erin Sutherland had with an older child) would place any mother immediately in a high risk category.

"What is more any case of serious post-natal depression should normally be considered and assessed for urgent admission to a specialist in-patient unit for intensive treatment."

She said she had repeatedly raised concerns about the adequacy of specialist training and supervision for staff, and about the standard of assessment, referral and communication.

She said her understand was that problems she had raised had still not been properly addressed.

These included local services continue being run by medical locums with no "substantive" specialist doctors in the perinatal posts. Staff recruitment and retention were problematic and sickness rates remained very high, she said

She said it was a "failed service."

As the Mental Health Welfare Commission (MWC) launches an inquiry, Lothians MSP Neil Findlay said he had written to Health Secretary Shona Robison on May 16 highlighting his concerns about the perinatal service at St John's, but had yet to receive a reply.

Dr David Farquharson, Medical Director, NHS Lothian, said: "Managing risk is one of the most challenging aspects in caring for patients with mental health issues both in the community and in hospital.

"It would be premature to speculate about the conclusion of the review from the MWC, but any learning from it will be taken forward and immediately implemented. Dr Jane Hamilton has not worked with the Mother and Baby Unit at St John's Hospital in Livingston for five years."

Health Secretary Shona Robison said: "Issues relating to the quality of care and patient safety in the unit have been investigated by an expert group - that was both independent of NHS Lothian and the Scottish Government. That independent group of experts noted their satisfaction with the level of specialist knowledge and skills of clinicians in the unit and the standard and quality of care provided."

She said any lessons from the MWC probe will be implemented quickly, adding: "NHS Scotland will look closely at their findings to ensure everything possible is done to prevent tragedies like this from happening in the future."