Statisticians and critics have questioned the figures, particularly as the government didn't provide adequate sources or examples of how they reached the 43 percent figure, with many believing the number is significantly lower.
A summary of the government's statistics was later released, but only after Cameron made the claims to the media.
Update on PM's claim about cost of EU migrants' benefits: @UKStatsAuth says delayed evidence is 'disappointing' https://t.co/K80THGfEHq
— Full Fact (@FullFact) November 11, 2015
Fact-checking website Full Fact made an official complaint to the watchdog, which resulted in heavy criticism from the Statistics Authority.
The Authority's chair, Sir Andrew Dilnot, wrote a letter saying the government's handling of the issue was "disappointing" and "unsatisfactory".
"It is disappointing that this [summary] was not available at the same time as the figures were released."
"The Code of Practice for Official Statistics expects that 'statistical reports should be released into the public domain in an orderly manner that promotes public confidence and gives equal access to all' and that producers should 'publish details of the methods adopted'. The release of these statistics without the subsequent accompanying background material explaining the methodology used, made it hard for those interested to understand and scrutinize the statistics, which was clearly unsatisfactory."
"UK Statistics Authority officials will have further discussions with those involved to avoid the recurrence of such problems," Sir Andrew wrote in the letter seen by UK newspaper the Independent.
Critics of Cameron have accused the PM of withholding the sources and methodologies used to boost the prime minister's push for EU reforms.
It's finally arrived. The DWP has published its stats on benefit claims by European migrants to UK https://t.co/ImmKjnl1MW
— Paul Waugh (@paulwaugh) November 10, 2015
The government has called for measures to be introduced to make it harder for EU migrants to access British public benefits within the first four years of their time in the country, following fears that some EU nationals may be engaging in benefit tourism.
This isn't the first time Cameron has been reported to the Statistics Authority, with the watchdog last year correcting the PM over unjustified claims he made about the majority of new jobs being given to British people rather than foreign workers.
The Authority at the time said that the statistics used by the government didn't refer specifically to new jobs, which meant Cameron's claim was unjustified.
