Dr Zudin Puthucheary, council member of the Intensive Care Society and a critical care consultant, told Sky News he was "scared and angry" as the COVID-19 crisis takes its toll on hospitals - notably in London.
Dr Puthucheary, who also works at the Royal London Hospital, said there is a shortage of critical care nursing staff and intensive care units "are full beyond bursting".
"There are more patients than we have ever had and we have less staff than we have ever had," he said.
"We've cannibalised staff from all around the hospital - volunteers are pouring in to try and look after these patients and deliver the best care we can.
"Staff are breaking themselves to make this happen and keep our patients safe - and it's not going to be enough."
He added that seven out of 10 people who go into intensive care with coronavirus will survive - meaning that 30% of people will die.
And he warned that those who survive could still face long-lasting damage, saying: "Seventy per cent of people will be disabled for years to come because they lose so much muscle - you lose almost two kilos."
Dr Puthucheary said the average age of intensive care patients is 60 and 90% of patients were leading normal working lives before admission, with many people filling up intensive care wards aged just in their 40s.
"They look like me, they look like my wife and my friends - they have children the same age as I do," he said.
He also said the term "underlying health condition" is a "made-up term" which is "meaningless to our patients and meaningless to us - it doesn't mean anything".
Dr Puthucheary said the major incident declared in London signals that hospitals' decision-making capacity may be taken away.
"Staff is going to be the single greatest bottleneck for us and I don't know what the solution is - and that really scares me," he said. "We don't have enough critical care nursing staff. We don't have enough doctors.
"We have volunteers coming in, we have very senior doctors and doctors with no training coming in to support our nursing staff, but you can't just magic up a critical care nurse - it takes years and years of training."
And in a message to the public, Dr Puthucheary said: "I'm scared and I'm angry.
"I'm scared because we are reaching a point where someone might tell us we can't prioritise our patients above everything else - those decisions are going to be taken away from us and none of us have ever lived through that."
He added: "The legacy of this pandemic will destroy 2021 and continue to destroy the NHS.
"That's what I'm scared about - and I'm angry that people are not listening. We hear the TfL (Transport For London) footfall is twice that of what it was in the first wave - twice as many people out there doing things on a Saturday when they should be home."
Analysis by Sky News' technology correspondent Rowland Manthorpe shows people are moving about more in this current lockdown, than they did in the first - with the public seemingly used to bending the rules to suit them.
He continued: "I'm angry because we're talking about protecting the NHS and that's clearly failed - we should be talking about protecting the healthcare of the nation. That is what is suffering right now - not the NHS. The NHS is breaking in front of us and there is no plan to stop it breaking.
"We need to stop the health of the nation breaking - that's where we've got to.
"That's why I'm angry and that's why all of our staff are angry."