Pharmacists have heavily criticised plans to strengthen checks at the counter for entitlement to free prescriptions in England.
The Royal Pharmaceutical Society says asking pharmacists to police prescriptions could harm patient trust.
By 2018, a new database will be up-and-running for pharmacists to check before handing over a free prescription.
Ministers say these extra checks could save the NHS £150m a year, which will be ploughed back into the NHS.
Currently, pharmacists largely rely on people's honesty when dispensing medicines for free.
Patients should present an exemption certificate and/or sign the back of the prescription form to say that they are exempt of any charge.
The NHS Business Services Authority runs checks, but only after a free prescription has been issued.
The Department of Health says this is not timely enough, meaning the system can be abused.
An estimated 30m prescription items totalling around £237m are incorrectly claimed each year.
Prescriptions in England
You can get free NHS prescriptions if you are:
- over 60, under 16 or aged 16-18 and are in full-time education
- pregnant or have had a baby in the last 12 months and have a valid maternity exemption certificate
- have a specified medical condition and have a valid medical exemption certificate
- have a continuing physical disability that prevents you from going out without help from another person and have a valid exemption certificate
- hold a valid war pension exemption certificate and the prescription is for your accepted disability
- an NHS inpatient
You may also be entitled to free prescriptions if you or your partner receive certain allowances, such as income support.
Health Minister Dan Poulter said it was time to get tough on those who avoid paying their fair share towards the NHS.
"Claiming a free prescription when you are not entitled takes money away from other frontline patient services, and reduces the amount of money available to spend on patient care."
Chief Pharmaceutical Officer Dr Keith Ridge said the new measures aimed to strike the right balance between collecting charges and providing care.
But the body that represents pharmacists in Great Britain, the Royal Pharmaceutical Society, says the new system could get in the way of treating patients.
RPS Board Chair David Branford said: "This move to make pharmacists police the Government's unfair charging system is totally unacceptable to us.
"Our job is to put the needs of vulnerable people first and make sure they get the care they need."
Around 90% of prescriptions in England are currently dispensed free of charge.
Wales, Scotland and Northern Ireland have scrapped all prescription charges.