Medibank was worried that a negative backlash over changes it made to out-of-pocket expenses for its policies represented a "high risk" to its $5.7 billion ASX float in late 2014, a court has heard.

The Australian Competition and Consumer Commission claims Medibank, which listed on the ASX in 2014, misled consumers by not adequately informing them of changes to out-of-pocket expenses for diagnostic services in private hospitals.