A hospital is conducting an inquiry into "shocking" claims that a patient went without food and drink on a 12-hour ambulance journey to Inverness.
Patient Daniel Baldwin went without food and drink for 12 hours
The parents of Daniel Baldwin, 43, who suffered a stroke and brain haemorrhage while working in London, said he was left alone in the back of the vehicle.
Private ambulance firm Select took Mr Baldwin from King's College Hospital.
Hospital officials said they were shocked to hear the claim and were now reviewing their use of Select.
Select, which carried out about 50 trips to Scotland last year, said it would discuss the matter with the driver, the person who booked the ambulance and King's College Hospital before making any conclusions.
Patricia and Mervyn Baldwin, from Ballachulish, said their son was "treated like an animal".
Mr Baldwin had suffered the stroke and brain haemorrhage in October.
He underwent emergency surgery at King's College Hospital but wanted to be transferred to the Highlands.
The hospital arranged for a transfer to the high dependency unit at Raigmore in November.
But Mr Baldwin claims nurses said his son arrived in "a dreadful state".
Mr Baldwin said: "Daniel seemed not to have had anything to eat or drink for the entire journey. He was also in the back of the ambulance on his own for the whole time.
"Daniel was treated like some kind of animal. It would be illegal to treat a pig like that.
"Worse still, he wasn't even offered a comfort break - the nurses said he arrived soaked from head to foot and shivering with cold.
"We have nothing against the National Health Service - they've been fine.
"As far as we know, the only mistake they made is giving our son over to these people - if they deserve to be called people - who treated him in such a terrible, terrible manner."
Daniel's mother Patricia added: "He had nothing to eat, nothing to drink and no comfort break.
Mervyn Baldwin said his son was 'treated like some kind of animal'
"He indicated that the ambulance drivers had stopped for breaks twice.
"If he'd been a cow or a sheep he wouldn't have been allowed to go this long without any attention."
The couple have demanded answers from the people who looked after Daniel on his journey.
Jon Adams, general manager of Select Hospital Services, said: "We are aware of the allegations made about the treatment of Daniel Baldwin from King's College Hospital to Raigmore Hospital.
"We are investigating these allegations and will be replying to them as soon as our investigations are complete."
A spokeswoman for King's College Hospital said: "King's College Hospital is taking this allegation extremely seriously.
"The level of service appears to have been totally unacceptable and we will be reviewing our agreement with Select."
NHS Highland said Daniel's ordeal was "unacceptable", but added it was not responsible for patient transfers from other areas.
However, chairman Garry Coutts said it had already began looking into the allegations.
He said: "It's clear something has gone very badly wrong here and we've already written to the trust in England to ask exactly what's happened to make sure this sort of thing can't happen again.
Daniel Baldwin was transferred to Raigmore Hospital in Inverness
"It's important if patients are going to be transported long distances there is clear communication between the hospital they are leaving and ourselves."
Highlands and Islands Conservative MSP Mary Scanlon branded the treatment heartless, humiliating and degrading.
She told BBC Radio's Good Morning Scotland programme: "I think we need to look at whether we do have an adequate code of practice where a private ambulance is given a contract to transfer a patient 570 miles up to Scotland to ensure that they are transported with the respect and dignity that they deserve.
"I understand the driver had two stops, I also understand that he didn't open up the back of the ambulance to look at the wellbeing of the patient."
She added: "I'm pleased that NHS Highland and others will be investigating this case because I hope that no patient ever has to endure a journey like this again."