The author of a new report on the health insurance market has said the principle of everyone paying the same regardless of their health is under threat.

UCD economist Colm McCarthy, who compiled the report for Aviva Insurance, said community rating was not viable in the long term if there an insufficient amount of young people buy health insurance.

Speaking on RTÉ's News at One, Mr McCarthy said the composition of the decline in the health insurance market was worrying, with more young adults dropping cover.

He said the Government's aim of having universal health insurance by 2016 was becoming more difficult, with the gap from now to the UHI model getting larger.

On the increased charges for private health insurance holders using public beds, Mr McCarthy said he believed the consequent increase in premiums would be at least the reported 15% and possibly more.

He said insurers had a very small profit margin and would be unable to absorb more.