According to newspaper Correio da Manhã the incident took place Wednesday as the five-year-old was getting ready for a series of tests.

The doctor is said to have slapped the child, who is undergoing chemotherapy and radiotherapy, after he grew restless and became noisy.

She allegedly apologised for the slap immediately afterwards and blamed her actions on being anxious and overworked.

The boy’s parents have sent an email to the institution in which they said they would be taking official action.

The Institute has said an investigation has been launched into the incident.