The NHS's "insufficient" critical care capacity has been laid bare by the pandemic, with the UK having one of the lowest number of beds per head in Europe, NHS Providers has said.
The group, which represents trusts in England, is calling for a review of the health service's capacity.
The UK has 7.3 critical care beds per 100,000 people, compared to Germany's 33.8 and the US's 34.3, analysis found.
The government said it was investing £72bn in the next two years in the NHS.
The east of England, South West and South East are areas of key concern.
"The UK is towards the bottom of the European League table for critical care beds per head of population," NHS Providers said.
The group added that the UK had comparatively fewer critical care beds than France, Italy, Australia and Spain.
"It's neither safe nor sensible to rely on NHS hospital trusts being able to double or triple their capacity at the drop of a hat as they've had to over the last two months, with all the disruption to other care and impossible burdens on staff that involves."
Seeking a review into critical care capacity in England, the organisation said it wanted the government to commit to providing additional finances in areas where it was needed.
"There have been too many reviews of NHS capacity in the past where huge amounts of time have been wasted because the government has not been willing to fund the results of what's been found," the group said.
When reviews and a public inquiry at some stage look at lessons to be learned from the handling of the pandemic in the UK, the question of the readiness of the NHS is sure to be considered.
NHS Providers has highlighted one key part of this - the relative lack of critical care beds in hospitals, reflecting in part insufficient investment going back many years.
The UK has fewer hospital beds for seriously ill patients relative to the population than leading European economies such as France, Germany, Italy and Spain.
So going into the pandemic the health service was in some ways not as well resourced as it might have been.
The NHS coped astonishingly well last April and in the most recent surge, and hospitals were not overwhelmed.
But sufficient critical care beds were created for Covid patients only by using wards which could not therefore be used by others - much routine and non urgent care had to be postponed.
The argument now being made is that there needs to be a review of what is needed as a safety net for future crises - and funding to go with it.
A Department of Health and Social Care spokesperson said: "The government is determined to back the NHS in every possible way in its fight against this virus, investing £52bn this year and £20bn next.
"This is on top of £9.4bn capital funding to build and upgrade 40 new hospitals and £3bn earmarked for supporting recovery and reducing the NHS waiting list."
They added that the government was on track to deliver 50,000 more nurses by the end of this parliament.