A huge, previously unreported waiting list of more than 90,000 patients has been revealed by one of England’s most troubled trusts. It comes amid an intense national drive to tackle politically sensitive waiting targets.

An investigation into waiting times performance at Barking, Havering and Redbridge University Hospitals Trust found that 92,236 patients had not started treatment at the end of August, 61,143 of which had been waiting past the national 18 week limit.

The revelation came as senior NHS figures confirmed that a government push to bring down elective backlogs would rely heavily on performance in September despite previous intentions that the bulk of the work would be cleared by the start of this month.

It is understood that if this month’s drive falls short, it could threaten health secretary Jeremy Hunt’s commitment to meet headline waiting targets by the end of this year.

Barking’s backlog figure, if accurate, would represent a significant addition to the total number of patients in England who have been waiting more than 18 weeks.

In June, the latest month for which national referral to treatment data was available, there were 189,571 patients waiting over 18 weeks across England.

However, Barking was among five providers for which figures were not included in the June data.

The trust has not reported its waiting list since January because of data validity issues, identified when a new patient administration system was introduced in December.

Trust chief executive Matthew Hopkins said there were “significant issues with the way we manage waiting time data across our hospitals”.

He added: “This is completely unacceptable and, as the new chief executive, I am absolutely determined that all our patients are seen as quickly as possible.

“We will be contacting patients affected with their new appointment dates and providing extra operations at both Queen’s and King George hospitals to tackle this as a priority.”

Queen's Hospital Romford

Barking, Havering and Redbridge plans to conduct more operations at Queen’s Hospital to reduce the backlog

The trust will not start reporting RTT data until January and does not expect to meet elective waiting targets until mid 2015.

Waiting times expert Rob Findlay said: “This trust is unlikely to be alone in having a backlog up to the end of August. I hope that they, and others, feel able to carry on treating the longest waiting patients first, even if that means a continued breach of the admitted patient target.”

The news comes amid a sustained national drive to tackle elective waiting lists. In May, the English waiting list exceeded 3 million for the first time since 2008 and in June the Department of Health released £250m to help providers clear planned care backlogs.

Official guidance released in July said national bodies expected providers to complete the bulk of this extra work by the end of August, leading to provider complaints that this coincided with the peak of staff annual leave.

However, NHS sources this week confirmed that the push would continue through September.

Some trusts are set to breach the waiting time target as they treat their backlog of longer waiters, while other areas face a more fundamental capacity problem.

Some senior figures from both commissioners and providers were sceptical that the national backlog would be cleared and waiting targets reached by the end of this month. One source told HSJ that messages from the national bodies involved were “increasingly hysterical [in] tone” and suggested a lack of confidence.

Others were more optimistic. NHS England Essex area team director Andrew Pike said in his area there would be a worsening of performance against waiting targets in August and September “in order to achieve [the target] from October”.

He said: “There has been an almost deliberate clearing of the tail of the backlog. If you are bringing in more people to clear the backlog, you are bringing in more people who have breached the target so the figures get worse before they get better.

“By October we should be back to 90 per cent of all patients having their complete waiting time and treatment within the 18 weeks across Essex.”

A senior source involved in national work to tackle backlogs suggested there were grounds for both optimism and caution on the overall waiting list size.

On one hand, preliminary results of work to validate the quality of trust data showed there had been some double counting and waiting lists were in fact smaller than they appeared.

On the other, three large trusts - including Barking - were still not submitting waiting data to the national dataset. The source expected the two factors to largely balance out in the national figures.

In a supplementary statement issued following initial publication of this article, Barking chief executive Matthew Hopkins emphasised that it would be wrong to assume that the waiting list figures reported to the trust’s board equated to the number of patients affected.

He said: “We know there have been issues with our data, which is why we are undertaking a validation exercise.”

This story was updated at 5pm, on Wednesday 10 September 2014