Online appointment booking service HealthEngine has rejected claims that it has been sending text messages to patients encouraging them to download its app without the consent of their general practice.

A medical centre group in Victoria says three of its patients received a text message purporting to be from one of its clinics immediately after booking an appointment through the practice's own booking system, and none of them had registered with HealthEngine.

HealthEngine said the texts were part of its in-practice patient communication service, which the practice would have given written or verbal consent to use when it signed up with HealthEngine.