The House of Commons Library has stepped back from a major row with Downing Street after heavily criticising David Cameron's use of NHS statistics.
Analysis released by the respected research unit dismissed the Prime Minister's claim that the "average waiting time" in NHS hospitals had fallen from 77 minutes under Labour to just 30 minutes.
It argued the data "did not support" the assertion, made during PMQs yesterday, describing it as a "simplistic reading" of statistics.
Labour seized on the assessment to accuse Mr Cameron of "cynical spin", while a furious Number 10 insisted the premier had been "100% accurate".
The research was taken down by the Commons Library this evening, and replaced with a statement reading: "The blog post 'Have A&E waiting times fallen?' has been removed by the House of Commons Library as it does not meet our expected standards of impartiality.
"A revised post will be uploaded as soon as possible."
The analysis had argued that Mr Cameron's claim related to a measure which "is not the most natural indicator of the 'average waiting time' in A&E".
Rather than looking at average waits for treatment - which has been "static save for seasonal variation" since the change in government - or total time spent in A&E - which has been "steadily rising" - Mr Cameron's figure related to the average time after arrival in casualty before patients are first assessed.
And rather than highlighting the "median" average, which "has remained more or less unchanged at around 10 minutes" since 2008, Mr Cameron pointed to the "mean" average, which showed a dramatic fall from more than 70 minutes to around 30 after April 2011, which was the date when time to initial assessment in A&E was designated as a "care quality indicator" and became subject to mandatory reporting.
The House of Commons Library said that evidence suggested that "the mean value here is not a good indicator of time to initial assessment in A&E, so we should rely on the median value to tell us what the typical time to initial assessment in A&E is... which does not show the trend that the PM refers to."
The assessment added: "It's plausible that the fall in the mean in April 2011 reflects an improvement in data collection, quality and reporting, rather than any genuine change in waiting times."
The analysis concluded: "The data does not show that the average time in A&E has fallen since 2008. Rather, the typical total time in A&E has risen (for admitted patients, at least), and the typical time to treatment has remained static.
"It is welcome that the rich data on the amount of time patients spend in A&E is becoming part of the wider political debate on the NHS. But in order for it to be useful and informative, it must be discussed in a way which fully respects the data."