During a professional network meeting, GPs raised concerns that work had not been undertaken to assess the impact of changing diagnostic criteria. The WHO is currently considering a switch to HbA1c-only diabetes diagnosis.
Dr Karet, a GPSI in diabetes in West Yorkshire, said the issue was out of the hands of healthcare professionals.
'This is a worldwide issue and it is motivated by the clinical chemists, not by clinicians,' he said. 'I think it is pretty much a done deal.'
University of Leicester research presented at the conference suggested that introducing a 6.5 per cent HbA1c cut-off for diabetes diagnosis would double the number of people diagnosed with the condition.
But Dr Karet said that how changes in diagnosis would affect diabetes rates was unclear and that official estimates were being kept under wraps.
'The people with the projections have been told in no uncertain terms not to disclose the information because it is politically sensitive,' he said.
A team from the University of Birmingham presented a study suggesting a 6.5 per cent HbA1c cut-off for diagnosis had low sensitivity and specificity.
'Further comparison of data with WHO criteria is required before clinicians will feel comfortable adopting it as a single diagnostic test,' they said. 'Further validation in other populations and consideration of a combination of glucose and HbA1c are required.'