Road safety advocates say breathalyzers are so reliable now that the right to also have a blood test taken is no longer always necessary.
A select committee is considering changing the law to close a loophole in drink driving laws.
The change was proposed after a man blew a failed result on a breathalyser last year and then asked for a blood test.
The man's veins were so damaged from drug use, the police were unable to get a proper sample and the man walked away.
The Automobile Association says that's unacceptable.
It says breath tests are reliable and people should not be able to escape punishment simply because they cannot give blood.
Alcohol Healthwatch agrees the loophole needs to be closed.
However, the Law Society says everyone deserves the right to challenge breath test results even if that means taking them to a hospital to have blood taken.
Its spokesperson Jonathan Krebs says the tiny number of people abusing the law is not a good enough reason to change it.