Parents left shattered as court rules their 8-month-old baby should be allowed to die.

When Charlie Gard was born on August 4, 2016, his parents believed their baby was “perfectly healthy”.

When their little boy’s health began to decline eight weeks after his birth, Chris Gard and Connie Yates took him to hospital. Charlie hasn’t been home since.

Charlie was diagnosed with a rare genetic disorder called mitochondrial depletion syndrome, a condition that causes progressive muscle weakness and brain damage, and he was soon placed on a ventilator to help him breathe.

The family's only hope was to raise money to fly Charlie to America from the UK to try an experimental new medication that could give their son a chance at a "healthier, happier life".

"We strongly feel as his parents that Charlie should get a chance to try these medications. He literally has nothing to lose," mum Connie wrote on a GoFundMe page for Charlie.

The campaign raised almost AU$2 million.

Now, a court has ruled that Great Ormond Street Hospital, who are treating the now eight-month-old, is allowed to switch off his life support, BBC reports.

Judges at the London-based High Court went against Charlie's parent's decision, ruling that, "it is in Charlie’s best interests [to]...withdraw all treatment save for palliative care to permit Charlie to die with dignity."

The judge added that the experimental treatment Charlie's parents wanted to fly to the US for could "not reverse Charlie's brain damage" and that while taking part in the research might benefit medical science, it "could not benefit the youngster".

Justice Francis thanked Charlie's "brave" parents after handing down the verdict.

"I want to thank Charlie's parents for their brave and dignified campaign on his behalf, but more than anything to pay tribute to their absolute dedication to their wonderful boy, from the day that he was born," he said.

Dad Chris, who had his dying sons' favourite toy monkey tucked into his suit, yelled "no" as the judge read his decision.

Mum Connie also broke down in tears when she heard her son would be refused further treatment.

The couple - who are both aged in their early 30s - are now considering their options for appeal.

"Connie and Chris are facing every parent's worst nightmare," solicitor Laura Hobey-Hamsher said in a statement on behalf of Charlie's parents.

"They are struggling to understand why the court has not at least given Charlie the chance of treatment in America."

Just a day before the judge announced his decision, Connie and Chris said they were "immensely proud" of their little boy.

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"We hope that we have done you proud by standing by your side and never giving up despite everything we've had to face!" they wrote on Charlie's Facebook page.

"We'd do it all again in a heartbeat because YOU are worth every ounce of pain and every single tear! You're our baby and we are your parents and we will do ANYTHING for you!

"We've got the money, we've got our passports, we've got the Dr who's got the medication...all you need is the chance (sic)."