Sixteen Irish charities say around €10m in clothing donations have been stolen from them by gangs in the last two years.
The charities are appealing to the public to bring their donations directly to their shops.
There is a lot of money to be made in reselling used clothing and Irish charities say their donations have been targeted by foreign-based gangs.
The Irish Charity Shops Association says these gangs are paying local van drivers €3-€4 per bag of clothing they collect.
The charities say they are losing donations in three ways - their donation bags are being stolen from doorsteps; their clothing bring banks are being broken into, and through the circulation of fake collection bags and leaflets.
The Irish Charity Shops Association says there are a number of ways people can ensure that they are filling a donation bag for a legitimate charity.
They can check that the bag has an address and landline telephone number, that it has registered charity number issued by the Revenue Commissioners, and that it bears the association's logo.
However, the ICSA says ultimately the only way to make sure donations reach the charity shop is to bring it there personally.