Intensive care for coronavirus patients is now being limited to those "reasonably certain" to survive, a major NHS London trust has conceded.

A department head at Imperial College Healthcare NHS Trust revealed on Sunday that fewer and fewer marginal patients are being selected for ventilator treatment because so many serious cases require a fortnight on the machines.

It comes as the NHS faces the toughest week in its history, with the deputy chief medical officer, Dr Jenny Harries, warning that the number of deaths will increase.

Imperial College Healthcare acknowledged that "very poorly patients with coronavirus may need to be on a ventilator for extended periods", adding that "for some patients this would not be in their best interests", but denied that people are being denied care due to capacity problems.

The statement amounts to the first admission that NHS doctors have significantly tightened their intensive care admission criteria since the start of the outbreak.