The organisation said that analysis of leaflets distributed by bogus collectors, records kept at Companies House and arrest information suggested a common link between the outfits.
The leaflets look different because of varied colour schemes, but they all fall into five templates, using the same wording, layout and typography, Clothes Aid said.
Records held at Companies House reveal connections between operators who have published the leaflets.
"The director of company A and the director of company B lived at the same address," said Michael Lomotey, head of collection protection at Clothes Aid. "We think it is run by a handful of people."