The family of a mother who took her own life by jumping from the Erskine Bridge is to sue a health board for medical negligence.

The Crown Office is still ­considering whether to hold a Fatal Accident Inquiry into the death of Claire Donald, 37, in January 2011. She left a husband and two young daughters.

She had twice tried to commit suicide before and her parents and husband believe there was a failure to diagnose a severe psychotic illness, which is far more profound than what is normally described as post-natal depression.

It requires in-patient care, and they are convinced she should never have been released from the Mother and Baby Unit (MBU) at St John's Hospital in Livingston. They say "Claire's last cry for help," was effectively ignored after staff were told she had suicidal thoughts but did not take her back in or visit her.

Her parents Jim and Jan ­Waggitt and husband Graeme Donald are questioning the ­qualifications of certain staff. They believe some of her case notes were written up after her death, and do not accept NHS Lothian's investigations were truly independent or objective.

The Herald revealed in June that a doctor who sounded the alarm over the safety of patients in the MBU had been off work for four years through suspension and stress-related illness. Dr Jane Hamilton claimed she had been victimised as a result of her ­whistle-blowing.

Following legal advice, Mrs Donald's family is preparing to launch a civil action for medical negligence.

Mrs Donald was an academic high-flyer who went to Glasgow University at 16. Before having her family she worked as a software engineer in the banking sector. She had her second child in October 2010 and suffered what was thought to be post-natal depression, as she had after the birth of her first daughter.

Mr and Mrs Waggitt prepared a joint statement for The Herald along with their daughter's engineer husband Graeme.

The family said of the second illness: "This was far more extreme. She was very ill. She had gone to her GP, who prescribed anti-depressants. But she had started to have thoughts of 'running away', which was her way of saying she was suicidal.

"On Saturday, November 13, 2010, she went to throw herself in the canal at Falkirk near where she lived. She saw Graeme, who ran out looking for her (he did not see her) so she decided to head for railway lines to throw herself in front of a train, but got caught up in barbed wire.

"Somehow she came to her senses and handed herself into the police pleading for help. They admitted her to the psychiatric unit at Larbert Royal Hospital. She was kept in for three nights.

"On November 17, after only one night at home, she drove off to the Erskine Bridge. There was a young soldier there. He spotted her and went to stop her. He almost went over with her. He punched her to the ground."

She was sectioned under the Mental Health Act, and admitted to the specialist MBU on November 18. Eventually she seemed to be progressing and began to be allowed day passes, going back in at night. She was allowed to stay out over Christmas and New Year.

"We had been assured by all staff we spoke to that Claire would get better and she would not be allowed out until they were 100% sure this was the case. But in January whilst at home, her thoughts of 'running away' returned."

A health visitor who saw Claire at home told her husband to phone the MBU.

"He got a nurse who talked to Claire and diagnosed her on the phone and told her she could up her dose of anti-depressants.

"It was said later it could have been detrimental to take Claire back into the MBU, but it was left to her husband to monitor her condition. It was also said a nurse had delegated another nurse to phone later. There was no phone call and three days later Claire went back to the Erskine Bridge and took her life."

The family sees this phone call as Claire's "last cry for help". Her mother was told it would have been difficult to get someone out to visit on a Friday afternoon as she lived outwith the MBU's catchment area.

The family has passed all the information to the police and the Crown Office in an attempt to secure a fatal accident inquiry. A spokesman said this was still being considered by the Scottish Fatalities Investigation Unit.

The Herald contacted Dr Jane Hamilton, who is still off work. She said: "My heart goes out to this family, but I really can't comment."

A statement from NHS Lothian added: "An initial full independent investigation into the care Mrs Donald received was carried out in late 2011 and found that the treatment did not significantly fall below the standard of acceptable care. It suggested some areas for improvement and we implemented these as part of an immediate action plan."

Dr David Farquharson, Medical Director of NHS Lothian, said: "A full independent investigation into the functioning of the MBU was carried out last year. The investigation found that the MBU was staffed by clinicians with the expected level of specialist knowledge and skills and the team functioned well.

"It found that the quality of care given to mothers and babies, including safety, was of a standard to be expected and that there were examples of good practice where expected standards were exceeded.

"Whilst there were some suggested areas for improvement, none of these issues compromised the safety and quality of the care provided. The findings of this investigation have been shared with Mrs Donald's family and the procurator-fiscal."