The storm broke out just hours after the party and leader Nigel Farage launched its Scottish manifesto, where those attending the event were greeted by activist Jack Neill.
Mr Neill, a former general election candidate in Kirkcaldy and Cowdenbeath, helped launch the 30-page election prospectus.
But, in a series of photos posted online, he appears smiling at the camera with his face blackened.
In one photo, which has also been posted on his Facebook page, Mr Neill wears a curly wig and bow tie as he poses with a mug in front of a Union flag.
Other snaps show him apparently in the bath, again with the blackened face and the clown’s nose.
Mr Neill was given a key role as Nigel Farage and David Coburn launched the party’s Holyrood manifesto at an Edinburgh hotel on Thursday.
Race equality campaigners condemned the pictures.
Mr Neill confirmed he had posed for the pictures, but said: “It was a joke. It was nothing to do with the party. It was something that one does in their spare time. It was for entertainment purposes.”
Nabirye Balyejusa, manager of anti-racism project SCOREScotland, described the former candidate’s actions as ‘quite hateful’.
Ms Balyejusa told The Herald: “Mr Neill is simply dredging up negative black stereotypes and his behaviour is quite hateful.
“This kind of conduct keeps everyday, drip-drip racism alive and well.
“It makes the work we do, for example with our young people to build their self-esteem and self-confidence, that much harder.
“Blackening faces for a laugh and entertainment is riddled with negative and extremely offensive connotations. It is nothing more than an excuse to make cheap fun at black people.’
The Scottish Liberal Democrats called on Mr Neill to apologise and Ukip to suspend him.
A spokeswoman said: “There is nothing funny about this. Jack Neill should apologise and Ukip should suspend him immediately.
“Political parties should be celebrating the diverse backgrounds of Scots, not encouraging people who think taking snaps of themselves in racist poses is acceptable on any level.”