Charities should ask for proof that their insurance brokers have registered with the Financial Services Authority, which takes over as the industry's regulator in two days time.
Sector specialist broker MCIS has said that many brokers have yet to register. This could leave thousands of charities without insurance cover.
The firm says charities should request confirmation from their brokers that they have the necessary authorisation for the 14 January deadline.
"It's a huge issue and comes at a time when many charities' efforts are tied up in accountancy year-ends and Christmas appeals," said MCIS chairman Roger Smythe. "Insurance sources say that out of 14,000 insurance intermediaries that initially registered with the FSA, 4,500 have failed to apply for authorisation. We believe many did not register at all."
MCIS says umbrella bodies, such as the Charity Finance Directors' Group, should encourage brokers that work with charities to register.