Priority managing director Louise Walters said: "We went to the exhibition and found the stand being built. They did not know it was our design until we told them but we said they were infringing the copyright law and should pay us."
A spokeswoman for Profile 22 said the company was keen to solve the dispute.
"Because we are the people that unknowingly used the design we are anxious to sort out the copyright,
Walters believes the exhibition design industry is blighted by copyright problems. "The trouble with our sector is that designs are offered on a speculative basis. You get a note eventually saying the client decided not to use your work on this occasion but you don't know if they will then go ahead and use it,