An NHS trust has launched an investigation after claims that a heavily pregnant patient was dragged from a seat and pinned to the floor face down by staff were made using social media. Three members of staff are said to have held the eight-and-a-half months pregnant woman on the floor after dragging her to the ground in a London psychiatric hospital.

The incident was said to have taken place at a mental health unit ran by the Central and North West London NHS Foundation Trust (CNWL). Bosses at CNWL have removed a member of staff from clinical duties while the investigation takes place.

The BBC reported that the incident took place on Sunday, 10 July, whilst a former adviser to the health secretary on patient safety was an inpatient at the secure unit. Alison Cameron, who posted about her experiences to Twitter, said the woman was being verbally aggressive but had not made physical threats to staff.

"A male nurse came marching over from the treatment room to the dayroom," the BBC quoted Cameron as saying. "He was threatening the woman saying 'If I hear your voice again, I will, I will…' and without finishing his sentence, he physically manhandled the woman from her seat to the floor. Three other members of staff then pinned her down."

Cameron, an associate at the London-based King's Fund and an expert on patient safety, has reported her concerns to the Care Quality Commission (CQC). The BBC says they have not named the hospital to protect the pregnant woman's identity.

In a statement, CNWL said it acted as soon as they heard of the allegation. "Witnesses (staff and patients) are being interviewed to find out what happened. We want to know why restraint was necessary, because it is always an extreme event, even when occasionally needed.

"After the incident, a doctor examined the woman in question and she was fine. We are working with her and her family about the incident and helping her from here."