Patients are enduring increasingly long delays before having some of the most common forms of surgery, according to official data that casts serious doubt on David Cameron's pledge to keep NHS waiting times low.

New research by the Patients Association also shows that fewer patients are undergoing planned operations such as joint replacements, cataract removal and hernia repairs, as the NHS tries to make £20bn of efficiency savings at a time when demand for healthcare is growing.

A report from the association, based on information supplied by 93 of England's 170 acute hospital trusts, found that waiting times for a range of elective operations rose between 2010 and 2011.

The average wait before having a new knee fitted rose from 88.9 days to 99.2 days, while patients needing hernia surgery typically waited 78.3 days in 2011 compared with 70.4 the year before. The delay before the removal of gallstones increased over the same period, by 7.4 days, as did the delay before having a new hip (6.3 days longer), hysterectomy (three days) and cataract removed (2.2 days).

Smaller numbers of patients also had surgery for all these procedures over the same period, according to responses from hospitals to freedom of information requests submitted by the association. Trusts that supplied figures jointly performed a total of 18,268 fewer operations for these conditions in 2011 than in 2010, with those blighted by worsening vision, especially older people, most affected.

Hospital waiting times Photograph: Graphic

Surgeons and health charities voiced concern that patients' health and wellbeing was being damaged as they were being left waiting in pain and discomfort for treatment, or denied treatment altogether. "It does look as if this report has confirmed something we have been worried about for the last two years, that patients are waiting longer in certain trusts to receive the treatment that they require and that fewer patients are getting the operations they need," said Prof Norman Williams, president of the Royal College of Surgeons of England.

"We are very concerned about this and really worried because patients who do not get the treatment they need within an appropriate time could be storing up problems for the future."

A patient forced to wait unduly long for a hip replacement would be "suffering [and] in awful pain", Williams said.

The biggest fall was in cataract removals. Some 175,731 were performed in 2011, which was 14,267 fewer than in 2010 – a fall of 7.5%. Clara Eaglen, eye health campaigns manager at the charity RNIB, said it was "deeply concerned" by the findings. "We already know that some primary care trusts are refusing cataract operations or delaying operations, forcing patients to live with unnecessary sight loss and a reduced quality of life. Cataract surgery should be performed when consultants believe it is in the patients' best interest. Introducing arbitrary thresholds, which delay cataract operations, is a false economy," she said.

Waiting times for the eight types of elective surgery studied rose by 6% year on year, and the number of such procedures carried out over the same period fell by 4.6% – the second successive year those trends have been seen – said Katherine Murphy, the association's chief executive. "Patients are calling our helpline to tell us they are being left to wait in agony and that their desperate calls to the hospital for help are being ignored. We hear lots of talk from the government about waiting times falling but whilst this may be true in other areas, it doesn't address the problem in relation to elective surgical procedures," she said.

But the health department said data from every hospital trust showed waiting times were low and stable and more patients were being treated, including for conditions in the report. The document was based on "partial" data and did not reflect the situation across England, it added.

Health secretary Andrew Lansley said: "There are fewer patients than ever waiting a long time for treatment in the NHS. The number of people waiting over a year for treatment has reduced by two-thirds since we came into office and the average time patients have to wait for treatment is at the same level as two years ago."

"We publish waiting times for different areas of medicine and surgery once a month, every month. They show that the average time that patients wait in areas that cover the operations selected by the Patients Association such as orthopaedics, eye medicine and general surgery, have either fallen in the last year or remain stable at very low historical levels," he added.

Andy Burnham, the shadow health secretary, said Cameron had "not been straight with the public about waiting times in the NHS". He added: "After inheriting the lowest ever waiting times in 2010, it would now appear that the NHS has gone backwards for the second year in a row and that is clearly linked to his disastrous decision to reorganise the NHS at this time of financial challenge. The prime minister has made waiting times the central test of his stewardship of the NHS and, based on the emerging evidence, it is clear he is failing patients as they are left to wait in pain and discomfort."

• This article was amended on 19 April 2012 to correct the spelling of the name of Clara Eaglen, from Clare Eaglen.