The decision prompted an incandescent response from Royal Mail chairman Allan Leighton, who said: "This is a shoddy report from a grandstanding regulator who is looking to micro-manage the entire postal industry."
Postcomm investigated Royal Mail after three of its competitors -- Express, TNT Mail and UK Mail -- complained about various aspects of its competitive behaviour.
The regulator has concluded that Royal Mail did not appropriately separate its wholesale division, which provides access to competitors, and its retail division.
Nigel Stapleton, chairman of Postcomm, said: "Many companies working for different clients have 'Chinese walls' -- internal separation arrangements that prevent conflicts of interest and the exchange of confidential information between teams working on different projects. The commission is surprised that Royal Mail did not think it needed to do this in a fully professional manner."
Last week, Postcomm proposed fining Royal Mail £11m after finding it guilty of "serious breaches" of its licence in mail security and staff checks. Royal Mail is appealing to Postcomm against that fine.
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