Charlie Gard’s parents have ended their legal fight for their critically ill baby to be flown to the US for experimental treatment, saying it was too late for the process to work.

After a five-month court battle, they said at an emotional hearing on Monday that they were abandoning their fight for Charlie to receive the nucleoside bypass therapy (NBT) they hoped would bring about significant recovery. Their decision means that Charlie, who was born on 4 August last year with a rare genetic condition inherited from his parents, will shortly be removed from life support at Great Ormond Street hospital (Gosh) and will not live to see his first birthday.

After Grant Armstrong, acting for Charlie’s parents, shocked the packed courtroom in central London by saying that owing to to “extensive muscle atrophy” they believed he no longer had any prospect of enjoying a “meaningful life”, the baby’s mother, Connie Yates, read a statement.

As she tearfully paid tribute to the couple’s son from the witness stand and insisted that they had only done what any parent would do, friends, family, lawyers and members of the press also wept.

How new brain scans showed Charlie Gard could not be helped Read more

The hospital later made an unprecedented attack on US neurology professor Michio Hirano, who had led Charlie’s parents to believe he could be treated. In a statement it said Gosh had shared their hopes when Hirano said he had new evidence that Charlie might benefit from NBT.

But it added that they had learned with “surprise and disappointment” last week that he had neither looked at the child’s brain scans nor read the medical notes, other expert opinions or the judgement of the court. It added that Hirano “retains a financial interest in some of the NBT compounds he proposed prescribing for Charlie”.

In court, Yates spoke of the couple’s efforts to save their son. Supported by her husband, Charlie’s father Chris Gard, she said: “Mummy and Daddy love you so much Charlie, we always have and we always will and we are so sorry that we couldn’t save you but we weren’t allowed to. Sweet dreams baby. Sleep tight our beautiful little boy.”

Armstrong, who was also in tears as he again addressed the court after Yates had spoken, said at the conclusion of the hearing: “It doesn’t get rawer than that.”

Yates and Gard hugged and kissed court staff, supporters and relatives as they left the courtroom.

Emotions were also high outside the Royal Courts of Justice, central London, when the news filtered out. There was anger and tears among protesters who have kept up a noisy vigil with people chanting “shame on you, judge” and “shame on Gosh”. Members of US pro-life groups who flew over to side with Charlie’s parents could be seen holding hands and praying.

In the statement read in court, Yates and Gard paid tribute to the “second-to-none” care for Charlie at Gosh but nevertheless made clear their frustrations at the delays they believe scuppered their son’s chances of survival.

Yates said: “There is one simple reason for Charlie’s muscles deteriorating to the extent they are in now – time. A whole lot of wasted time ... our poor boy has been left to just lie in hospital for months without any treatment whilst lengthy court battles have been fought.”

She also maintained that Charlie, who is blind and deaf, had not suffered irreversible brain damage as the hospital has said and insisted that it was only the muscular atrophy that rendered the NBT therapy no longer worth pursuing.

Monday’s hearing had been expected to be a chance for Yates and Gard to present what they claimed was new evidence that showed the prospects of successful treatment for Charlie were higher than previously thought.

Timeline: Charlie Gard and his parents' legal battle to save him Read more

But the court heard that after new EEG and MRI scans were carried out that it was hoped would boost their case, a multidisciplinary meeting was held and experts concluded that Charlie had suffered significant muscular deterioration.

Among those at the meeting was Hirano, who had spoken in favour of Charlie having the NBT which he said had a minimum 10% chance of bringing about significant improvement in his condition. His evidence was expected to form the crux of Monday’s hearing before Yates and Gard decided to drop the legal proceedings.

According to the hospital statement, signed by its legal counsel, Katie Gollop, QC, its doctors had consulted with Hirano about possible NBT for Charlie last year and were seeking ethics approval to send him to the US. But he suffered seizures before Christmas that resulted in irreversible brain damage. Charlie’s parents disagreed with the hospital’s assessment and believed he could have been treated in the months that followed, but “there remains no agreement” on that.

“As the weeks have passed, the unstoppable effects of Charlie’s aggressive, progressive, depletive disorder have become plainer to see,” the Gosh statement said.

But when Hirano, backed by other doctors in Italy, said there was new evidence that NBT would work on the child, Gosh hoped that he was right. The professor took up the invitation that had been open since last December to come to the UK for the new court hearing. In its statement the hospital said it hoped that he and others whose medical opinions “had so sustained Charlie’s parents” would “find much upon which to reflect”.

Yates and Gard said in court that Italian and US doctors were still willing to give Charlie NBT but they had concluded it was not in their son’s interests. They made the decision to end their legal fight on Friday night but kept it to themselves so that they could spend time in private with their son over the weekend, away from the glare of the media, their counsel said.