A High Court judgment handed down on Friday has ruled that it is in the "best interests" of Archie Battersbee for his life support to be removed.
Mr Justice Hayden said that further treatment would be "futile".
"It compromises Archie's dignity ... and serves only to protract his death rather than prolong his life," he said.
Archie, 12, was found unconscious in his home in April with a ligature around his neck in what is believed to be a tragic accident.
His parents, Hollie Dance and Paul Battersbee, have been fighting against the wishes of doctors to remove his life support.
Doctors have argued that a "planned death" would be in Archie's best interests.
Ms Dance and Mr Battersbee plan to appeal the High Court judgment.
Ms Dance said today's ruling was "a crushing blow" for Archie and his family, and that it was not in her son's best interests to die.
"'Planned death' is another name for euthanasia, which is illegal in this country," she said.
"The 'planned' removal of the ventilator is definitely the worst thing that may happen from my point of view. I cannot see how this is in any way dignified.
"We disagree with the idea of dignity in death. Enforcing it on us and hastening his death for that purpose is profoundly cruel.
"It is for God to decide what should happen to Archie, including if, when and how he should die.
"As long as Archie is fighting for his life, I cannot betray him. Until Archie gives up, I won't give up.
"I am living every parent's worst nightmare. There must be change in the NHS and in the court system before another family has to go through what we have.
"We will be appealing this ruling and we ask for your prayers and support."
Andrea Williams, chief executive of the Christian Legal Centre, which has been supporting Archie's parents in their legal battle, said the judgment was a "devastating blow" for the family.
"Sadly, however, this is what we have come to expect from the courts in end-of-life cases," she said.
"What Archie's case has shown is that systematic reform is needed to protect the vulnerable and their families in end-of-life matters. Parents of vulnerable and critically ill children are being put through the mill at the most traumatic moments in their lives when what they need is compassion, support and respect from the NHS and the legal system.
"Behind the back of Parliament and the public, courts seem to have developed a concept of 'dying with dignity' which amounts to euthanasia in all but name.
"These sensitive ethical issues should be debated and determined in the democratic Parliament, not by judicial activists.
"Life is the most precious gift that we have.
"Anyone following this story over the past few months will have seen what it takes to challenge the will of hospital bosses once they have decided life support should be removed.
"This family have fought courageously to get to this point in taking a stand for Archie's life. We continue to stand shoulder to shoulder with them as they appeal this ruling."
At a hearing this week, Ms Dance described how her son had expressed an interest in Christianity and being baptised, and that, because of this, she felt he would not want a planned death.
"Archie was asking me to get him baptised over a few years before his accident, particularly after he started watching a lot of box fights on TV," she said.
"Many boxers pray for protection when they go into the ring. The more and more fights he'd watch with his brother, the more he would be nagging me to get him baptised.
"Every time we drove past St Mary's Church, he shouted out his most predictable line without fail, 'Mum when can we go and be christened in there'."
Archie would, she continued, "feel it is only for God to come and take him out of this world when the time is right for that.
"Until that time, Archie would want to remain with me and the rest of the family, even without knowing that himself," she said.
