Exclusive Hundreds of thousands of NHS patients who opted out of having their details shared with private companies under the controversial Care.data scheme would not be invited to a number of cancer-related screenings – a terrible effect of the gaffe-ridden scheme.

Care.data intends to extract GP information and share it with third parties. Under the "Type 2" opt-out, patients can dissent from the "disclosure of personal confidential data".

However, according to supplementary written evidence submitted by the Health & Social Care Information Centre (HSCIC) last week, patients who have registered a Type 2 objection "may not have understood that this will mean that as a result, they will not be approached for direct care services like e-prescribing, bowel screening, e-referrals or e-pathology reporting."

HSCIC, the oversight body, has said it will contact all individuals who have made a Type 2 objection to "ensure they fully understand the current implications. The body said it is "offering a solution which would not impact on their direct care." It said it is still "working through the detail" of possible solutions.

Dr Neil Bhatia, a Hampshire GP, told El Reg that nearly 2,000 of his patients have registered a Type 2 objection. Patient campaign group MedConfidential told us the lowest Type 2 opt-out figures they were aware of in a GP's practice were 650.

If those figures are extrapolated across the 8,000 GP practices in England, the number of patients HSCIC will be contacting could be as high as several million.

Phil Booth, co-ordinator at privacy campaign MedConfidential, described the effects of the problem as "terrifying".

"A patient should not be forced to choose between their privacy [and their] care," he said.

According to Booth the problem could be fixed by adding a line of code to GPs' systems that distinguishes between patients who do not wish to have their data shared with private companies under Care.data but still want their details passed on for nationally run cancer screening programmes.

The Care.data system was supposed to begin in spring 2014 but has been subject to a series of delays following a public outcry regarding the NHS's failure to properly consult on the programme.

Bhatia said that in light of the recent findings it is a huge relief the system has been paused. "Otherwise, because of this code there could have been some serious unintended consequences. People who did not want their data used for commercial purposes could have come to harm having missed out on screenings."

A spokesman from HSCIC said: "We are still working through the detail of possible solutions but have committed to providing patients with an option that recognises their objection but does not impact on their direct care." ®