The Irish Red Cross Society has claimed that other charities are using its emblem on their trucks and has complained to the Department of Defence.
Under Irish law, the Red Cross and the Army Medical Corps are the only organisations allowed to use the internationally recognised symbol.
A complaint about the practice was passed from the Department of Defence to the Office of the Garda Commissioner, Mr Pat Byrne, in October.
In a separate development in November, the Irish Red Cross Society wrote to Cradle, an Irish charity which assists children in central and eastern Europe, about a Cradle truck which the Red Cross claimed bore its emblem.
It asked Cradle to "take suitable steps to rectify this situation" and pointed out that the emblem cannot be used without the prior permission of the Minister for Defence, Mr Smith. The Department of Defence funds the Irish Red Cross Society.
According to the correspondence between the Red Cross and the Department of Defence, obtained by The Irish Times under the Freedom of Information Act, it is alleged another charity has also used the emblem, although it is not named specifically.
Yesterday, Mr Sven Braamark, a spokesman for Cradle, said the organisation owned no trucks and depended on hired haulage. As a result, he said, the charity knew little about what symbols were displayed on trucks.
"We don't own any trucks so it really has nothing to do with Cradle, but obviously if there is a problem we will deal with it," he added. He said if there was a problem with trucks improperly using the symbol, that was an issue for haulage firms.
In the letter to Cradle, the secretary-general of the Irish Red Cross Society, Mr Paul Lynch, said the use of the emblem by other organisations could jeopardise the work of Red Cross workers and compromise their reputation for neutrality.