Over one million more patients will be living with two or more serious long-term, life-threatening conditions by 2025, according to new analysis by the Royal College of General Practitioners (RCGP).
The additional care will cost the NHS up to £1.2 billion per year.
At the recent RCGP conference Chair Dr Maureen Baker highlight the "paradoxical situation" that delivering complex care to patients with chronic conditions is "most cost-effective in general practice yet the bulk of NHS money continues to go into hospital care".
The RCGP has pointed out that currently 90 per cent NHS patient contacts are made in general practice yet the share of the NHS budget that general practice received stands at 8.33 per cent.
Dr Baker said: "It is a great testament to modern medicine that nowadays we are much more likely to prevent or treat diseases that in the past killed people so early in their lives. GPs have played a pivotal role in this transformation.
"But this success has brought with it a whole new set of challenges to which the NHS is currently struggling to respond… We need an NHS that's properly set up to meet the complex clinical needs of people in the 21st century."