The father of an eight-month-old baby at the centre of a High Court life-support treatment battle has pleaded with the judge to give his son "a chance".

Doctors at Great Ormond Street Hospital (GOSH) in London believe it is time to stop providing life support treatment to Charlie Gard, however, his parents want to be allowed to take him to the US where they hope he can be treated.

Charlie suffers from a rare genetic condition called mitochondrial depletion syndrome which causes progressive muscle weakness and means that he is deaf and unable to cry.

Medics believe that further treatment would unnecessarily prolonging Charlie's suffering.

Chris Gard carried a toy of Charlie's in his pocket, and right, Connie Yates. Credit: PA

But his parents, Chris Gard, 32, and Connie Yates, 31, want to keep him on life-support and have fundraised more than £1.3 million to take him to the US where it is hoped he could undergo nucleoside bypass therapy.

Charlie's parents hope the treatment would repair their baby's faulty mitochondrial DNA and help it synthase again by giving him the naturally occurring compounds that his body isn't able to produce.

In court on Wednesday Mr Gard described himself as "Charlie's proud dad", adding: "My son is the apple of my eye and I would do anything for him and I want to give him a chance. He deserves a chance.

"It doesn't mean he should have to die because he will not be like another little boy running around."

Doctors in America have said they will accept Charlie as a patient if his treatment can be paid for. Credit: PA

Mr Justice Francis is analysing issues at a hearing in the Family Division of the High Court in London which began on Monday.

Mr Gard said he and Ms Yates believe in the treatment trial doctors in America are proposing.

"If there is no improvement we will let him go," he said.

"We just want to give him a chance. We know it is not a life. It is just having something there that could possibly improve him because he deserves a chance."

Ms Yates added: "I don't think he is suffering or I wouldn't be here."

She went on: "I don't think his brain function is as bad as what everyone else is saying."

Charlie Gard with his parents Chris Gard and Connie Yates. Credit: PA

It also emerged that Charlie's parents were described in an email as a "spanner in the works" by a doctor at GOSH.

Sophia Roper, a barrister representing the baby's parents, said the email had included the phrase: "The spanner in the works has been a parent-driven exploration of all alternatives internationally."

Ms Roper asked the intensive care specialist whether the email had been an "appropriate" way to talk about the couple's hunt for treatment.

The specialist accepted that the phrasing was "a bit clumsy".

Court proceedings were also halted for a short period on Wednesday after Ms Yates broke down in court, when a GOSH specialist gave evidence.

"Charlie has deteriorated hugely since he first came to us,'' said the specialist.

"The disease has affected his brain to the extent that he is completely ventilator-dependent.

"This situation is not a tolerable one to leave a child in.''

Mr Justice Francis has ruled that doctors involved in Charlie's care cannot be identified.

The hearing will resume on Friday.