Official documents show the police tried to get evidential blood tests for motorists who fail an alcohol breath test scrapped, to save time and money.
Police pushed unsuccessfully for the change during the formation of the latest road safety strategy and have not ruled out trying again.
Police say the time it takes to get a blood sample is long enough for a driver to sober up and avoid prosecution.
Superintendent Rob Morgan says removing the blood tests would mean fewer officers waiting for blood samples and more out policing the roads.
The Automobile Association says the blood test should be kept because it rules out any false readings from a breath tester.