A grieving mum claims her baby died because he became ill at the weekend and there were not enough hospital staff on duty to help him.
Merilyn Bartley, 46, said hours passed without a specialist checking on her five-month-old son Dominic.
The baby, who had had heart surgery at the Royal Brompton Hospital, was transferred to Barnet Hospital in North London to be monitored.
He arrived on a Friday evening and the next day his condition started to deteriorate.
His mum told the inquest into his death: "I was very worried as we hadn't seen doctors for a long time.
"There was an air of panic on the ward. I remember the nurses saying: 'There are no doctors'."
She said her family had been 'really badly let down'.
She added: "There was nobody to help. What do you do as a parent when your child is dying and there is nobody attending to him?"
Medical staff were meant to transfer Dominic back to the Royal Brompton for specialist care if he became unwell.
However the on-call consultant failed to examine the baby, even after his condition suddenly worsened.
On Saturday night Dominic stopped breathing and his face turned blue and mottled.
He was rushed to theatre but suffered a cardiac arrest and died on Sunday morning, just 36 hours after being admitted.
A specialist report eventually showed that his lungs had been overwhelmed by high levels of fluid.
On-call consultant Professor Anthony Costello said he would have ordered an urgent transfer back to the Royal Brompton if he had known about the problems.
But he claimed he did not have access to an echocardiogram machine, which would have flagged up Dominic's dangerously high blood pressure.
He also revealed that he did not get the results of vital tests until after the baby's death because it was the weekend.
He told the inquest: "You wouldn't get a report on a Saturday morning, it would have been the following week. Most hospitals at weekends don't get consultant reports.
"You need a good echocardiogram service and someone who is using it a lot. You won't get that on a weekend at Barnet.
"You don't want a child with any risk of complications in a district general hospital at a weekend."
Expert witness Professor Robert Tulloh said Professor Costello's decision not to examine the child was a 'failure to provide basic medical care', adding: "If he had taken action it would have prevented his death."
Coroner Andrew Walker adjourned the inquest until later this month so he could hear further evidence. But he expressed concern that 'crucial pieces of the jigsaw' at the hospital were missing because of low weekend staffing and a lack of specialist services.
He said: "You are missing a great deal of the facilities that you need at the weekend."
The Barnet Hospital Trust said it would be inappropriate to comment until the inquest was completed.