As of Wednesday official Government figures showed there were 10,798 positive coronavirus tests in the Black Country, Birmingham and Staffordshire up to July 1.
However this data only included results from people being tested in hospitals, what the Government calls Pillar 1, and not results from drive-through test centres and swaps sent by post (Pillar 2).
Pillar 1 tests are processed in Government laboratories while Pillar 2 tests are processed by commercial laboratories.
The Government has now released the number of cases recorded via Pillar 2 tests for the first time and has revealed that 4,739 more people than had previously been reported have tested positive in the region – an increase of 44 per cent to a new total of 15,537.
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Health officials have called for ministers to release accurate regional data following the decision to place Leicester back into lockdown after a spike in cases.
In the West Midlands the disparity was greatest in Staffordshire, with the county showing a 50 per cent rise in positive tests to 3,624 when Pillar 2 cases are included.
The number of positive tests in the Black Country went up from 4,158 to 5,734, a spike of 38 per cent.
Sandwell showed the biggest rise of the four boroughs, up 526 (48 per cent) to 1,620, while in Dudley there were 395 additional cases under Pillar 2, taking the total up 44 per cent to 1,294.
The data shows there are 30 per cent more cases in both Walsall and Wolverhampton than previously reported, with 1,449 and 1,471 cases respectively.
In Birmingham the number of Covid-19 positive cases went up from 3,361 to 4,758 – up 42 per cent.
It means that throughout the pandemic, a total of 4,739 coronavirus cases in the Black Country, Birmingham and Staffordshire have not been publically reported until now.
Public Health England says that Pillar 2 testing for the general public has made up the majority of confirmed cases since mid-May.
The British Medical Association had urged the Government to share more information about the virus.
Dr Chaand Nagpaul, chairman of the BMA Council, said: "The Prime Minister has talked about a ‘whack a mole’ strategy to tackle local outbreaks, but this is no use if the people leading the response on the ground – be they public health teams or local leaders – are not given the most accurate up-to-date data possible.
"This is crucial to allow swift action and to protect lives and the health service, and something that is not happening right now."