A mother seeking a cannabis oil supply to treat her sick son has said he is in a life-threatening condition.
Twelve-year-old Billy Caldwell was taken by ambulance to Chelsea and Westminster Hospital in London on Friday after his epilepsy seizures "intensified", a family statement added.
A batch of the banned drug used to treat him was confiscated from his mother Charlotte Caldwell at Heathrow Airport, and she said the Home Office would be held accountable if he died.
Ms Caldwell said: "This is beyond cruelty. We've now reached the point where Billy is too ill to travel to get his medication, but his medication is stored minutes away from where we're now living in London.
"Despite the best and honest efforts of the NHS, frontline doctors are fighting Billy's condition with both hands tied behind their back because the only medication that will be effective is the cannabis oil (with a banned component)."
She said the situation was described by doctors in Canada and Northern Ireland familiar with Billy's case as life-threatening.
The child, from Castlederg in Co Tyrone, started the treatment in 2016 in the US, where medical marijuana is legal.
He became the first person in the UK to receive a prescription after his local GP in Northern Ireland, Brendan O'Hare, began writing scripts.
However, there is no record of a health service prescription being dispensed.
Dr O'Hare was summoned to a meeting with Home Office officials recently and told to desist.
Ms Caldwell made the trip to Toronto and back with 12-year-old Billy to get a six-month supply to treat up to 100 seizures a day, but said border officials seized the oil.
She added: "Billy has had back-to-back seizures today, Friday.
"On his medication, which included the vital but banned THC component, he was seizure-free for more than 300 days."
She said her son was too ill to travel to Canada to get his medication.
"If Billy dies, which is looking increasingly possible, then the Home Office, and (minister) Nick Hurd, will be held completely accountable."