The agency had referred its work to the PRCA's Professional Practices Committee (PPC) after Manchester City Council accused the agency and its client, the operator of Manchester Arena, of astroturfing and using "outrageous" and "misleading" communications tactics to oppose a rival 20,000-seat arena proposal.
The PPC decided unanimously that FleishmanHillard Fishburn had broken no part of the PRCA’s professional charter and codes of conduct, and "had throughout its work advised the client in line with the PRCA’s requirements for ethical practice".
"The PPC considered carefully the evidence and has come to the conclusion that FleishmanHillard Fishburn has not breached any element of the PRCA Code of Conduct," PPC chair Claire Walker said in a statement to Fleishman.
"The committee found that FleishmanHillard Fishburn gave their clients sound advice in accordance with the PRCA Code of Conduct and was not responsible for misleading the public. The committee will not be investigating this case any further, and as such this case is now closed."
FleishmanHillard Fishburn UK and Middle East CEO Jim Donaldson, who is also the chair of PRCA's board of management, said: "We take ethics very seriously at FleishmanHillard and that is why we decided to voluntarily refer ourselves to an independent review of this work. We are very pleased with the ruling."
PRCA director general Francis Ingham added: "I commend FleishmanHillard Fishburn for being the first member in our 50-year long history proactively to refer themselves to the PPC. It shows the importance they place on ethical professionalism."