Labour’s pledge to deliver 40,000 extra weekly NHS appointments to reduce waiting times will create less than a fifth of the extra activity required, a new study has found.

In its general election manifesto, the party set a target of having 92% of patients begin routine hospital treatment within 18 weeks of referral by the end of this parliament.

This would be achieved by having neighbouring hospitals share waiting lists, supplying additional capacity from the independent sector, and incentivising NHS staff to work extra evenings and weekends.

But a new report by the NHS Confederation and healthcare consultancy Carnall Farrar has found the number of appointments promised – equivalent to two million a year – would only meet 15% of the target, if care continues to be delivered in the same way.

The NHS would in fact need to provide 33.6 million outpatient appointments by 2028/29 to bring waiting lists back to meeting the 18-week level, according to the report.

The 18-week referral-to-treatment target was last met for a month in February 2016.

An additional 5.1 million appointments would be needed this year alone to stop the waiting list increasing further, the report found.

There are currently 7.6 million care pathways for some 6.4 million individuals open that have not been resolved through treatment.

The demand for NHS services is increasing faster than the rate of funding growth, at an average rate of 3.8% per year, the report said.

It added that a focus on 65- and 52-week waits for patients has created “distortion” in how healthcare providers try to address concerns.

Among its recommendations, the report calls for greater use of digital platforms in waiting list management, and patients on the waiting list having their reason for treatment continuously validated, as well as increasing capital funding in NHS England to at least £14.1 billion annually.

NHS Confederation chief executive Matthew Taylor said: “NHS leaders share the Government’s ambitions to restore performance on the 18-week target by the end of this parliament.

“But to achieve this the Government will need to use the autumn Budget to deal with the short-term deficit that is leading to NHS organisations either cutting or freezing posts. This will inevitably impede efforts to increase productivity and reduce the waiting list.

“We also know that the Government’s intention of paying NHS staff time-and-a-half for weekend and evening shifts to clear the backlog doesn’t go beyond what many NHS trusts are already paying. So this alone won’t cover the shortfall.

“Ultimately, we know that, in order to keep up with the healthcare needs of the population, the NHS needs reform, not just ever more activity. This means shifting to earlier, more preventative services – including primary and community care – to slow the rise in demand for healthcare.

“It will also mean boosting productivity through using modern technology and having buildings and equipment that are fit for the 21st century.”

Hannah Farrar, chief executive of Carnall Farrar, said: “The Government putting this at the heart of their agenda is promising; however, the challenge in achieving it when it hasn’t been sustainably met in over a decade shouldn’t be under-estimated.

“Forty thousand more operations is an important element but a step-change in the Government’s approach is also needed.”