The mother of a teenager who died while under the care of heavily-criticised Southern Health NHS Foundation Trust has been called a "vindictive cow" in a voicemail message apparently left by a member of the trust's staff.
Dr Sara Ryan has been campaigning for those responsible to be brought to account following the death of her son, Connor Sparrowhawk, known affectionately as Laughing Boy (LB).
An inquest jury ruled in October that neglect contributed to the 18-year-old's death after he drowned following an epileptic seizure at Slade House in Headington, Oxfordshire.
The message was left on Dr Ryan's workplace voicemail on Friday April 29 by a woman who said she worked for Southern Health.
She can be heard to say: "I work for Southern Health and I feel awful that you lost him. I'm so sorry that you have done, it's tragic, and I hope you find some closure after the report, the issue of the GM CQC report today, but I do think you are being very vindictive.
"I think you are a vindictive cow, on TV all the time, slating the NHS and Southern Health."
Dr Ryan said in her online blog: "The call is vitriolic, nasty and beyond inappropriate. But it's simply part of a set of improbably, inappropriate, nasty and worse responses we've endured since LB died.
"Evidence of a system in which defensiveness, bullying and family crushing flourishes."
A Southern Health spokesman said it would carry out an internal investigation into the call.
He said: "We have been made aware of the phone message through social media, and the content is deeply concerning. The Trust cannot condone such behaviour and we take matters like this extremely seriously.
"We urge anyone with any information to get in contact with us so a full internal investigation can take place."
Shadow mental health minister Luciana Berger called on Tuesday for the chief executive of Southern Health to be sacked after the Care Quality Commission (CQC) report published last week found the trust was still failing to protect patients from risk of harm.
An independent investigation found in December that it had failed to investigate hundreds of deaths since 2011.
Ms Berger said the CQC report suggested "very little" had been done to improve the performance of the trust.
Health Minister Alistair Burt admitted the report made for "disturbing reading" as he said the Government had not ruled out the possibility of an inquiry.