The number of people facing longer waits than they should for hospital treatment in England has more than doubled since 2012.
A key target waiting time of 18 weeks is not being met for more than 350,000 patients, resulting in a 163% rise in the space of four years, a BBC analysis found.
The total number of people on the waiting list is 3.7 million.
Figures for Wales and Northern Ireland, provided by the Royal College of Surgeons, show they have also seen a rise.
The increase between November last year and the same month in 2012 was almost three quarters for Wales, while a similar comparison for the month of September for Northern Ireland showed a 96% hike.
President Clare Marx said: "We cannot forget that behind these statistics are potentially very ill and anxious patients who are being made to wait far too long for treatment.
"This is the true impact of the serious financial pressure we've seen the NHS come under in recent months."
Waiting list figures for December will be published on Thursday. Last month, in the wake of the figures released for November, health service managers warned the NHS had reached a tipping point.
The NHS Confederation, which represents managers across England, said it was time the Government accepted "limited investment" has "consequences".