The number of patients now waiting for more than 18 weeks for an elective operation has shot up 80 percent in just a year, according to a report by the Patients Association.

The total number over-shooting the legal 18-week target in 2015 was 92,739, compared to 51,388 patients 2014. Excluding the figures for bariatric and gender operations (which weren't collected last year), this represents an increase of 79.5 percent, it says.

Also, 77 percent of trusts are failing to notify patients of their rights under the NHS Constitution when the 18 week limit has been missed, the report notes.

The research - taken from 78 percent of 112 trusts responding to freedom of information requests - also found that average waiting times for five procedures (hip replacement, knee replacement, hernia, adenoid and tonsillectomies) exceed 100 days, representing the highest average waiting time in the six years data has been collected.

Also of note, trusts cancelled an average of 753 patient surgeries 'on the day' last year, the most common reasons for which were equipment shortages and/or lack of beds, it said.

The report concludes that "too many patients are waiting too long for surgical procedures," stressing that, "behind waiting time statistics there are patients who are forced to put their life on hold, suffering psychological distress, pain and having to suffer the financial burden of in many cases not being able to work".

However, an NHS England spokesperson said there are "major issues" with the report that it has significant concerns.

It argues that the claim that 'the number of people waiting over 18 weeks for elective surgery is up by almost 80 percent' is "statistically flawed, in that it appears to have been calculated by directly comparing results from the 2014 and 2015 surveys (despite acknowledgement that there was a higher response rate in 2015)".

"We have significant concerns about this report which is both misleading and statistically flawed and is based on a fundamental misunderstanding of the RTT performance standard," NHS England said in a statement.

"Waits for an NHS operation remain close to an all-time low - down from a maximum wait of 18 months over a decade ago to 18 weeks now, with the average wait less than 10 weeks," it insists, adding that "last month more than nine out of ten patients were waiting less than 18 weeks to start consultant-led treatment".