Fianna Fáil leader Micheál Martin has told the Dáil that thousands of people across Ireland are receiving letters telling them their medical cards are being taken from them.
Mr Martin said the issue is affecting the most medically compromised, including young children, adults with serious illnesses and the elderly.
He asked Taoiseach Enda Kenny if he would reverse this policy.
Mr Kenny said that 43% of people now have access to free medical care through medical cards and GP visit cards.
He said there has never been an automatic entitlement to a medical card based on a person having a specific condition, such as cancer.
However, he added there is a system allowing the HSE to provide emergency medical cards within 24 hours.