The warning followed reports that unauthorised people were collecting money in Belfast and County Tyrone.

The mental health charity Mencap said two men seen collecting money outside a supermarket in the Knocknagoney area of Belfast were not connected to the organisation.

Police said that street collectors should possess a permit from the PSNI.

Mencap events manager Ciara Gallagher said such activities cheated legitimate charities of money and undermined the work of genuine volunteers.

"It's very disappointing from the charity's point of view that people would abuse our name," she said.

"The thing that concerns me most is the good that the majority of people do can be dented by something like this."

Mencap has urged people to check the identity of charity collectors before giving them money.