The Irish Medical Organisation has vowed that doctors who received payments from the Government in relation to ineligible medical card holders will not repay the money until an independent investigation is carried out.
The so-called "ghost" payments relate to medical card holders who had died or moved to another health board area.
Some doctors continued to receive payments for these patients because of inaccurate medical card records.
The Government has claimed that every doctor owes it an average of €3,400, but the IMO has queried this figure and has vowed not to repay the money until an independent body establishes the exact amount owed.
Spokesman James Reilly said: "We were told it was originally €20m, then €12m, maybe €6m and now the papers are reporting €8m. We want to see the facts as elicited by an independent third party."