Client entertainment is one thing, but asking employees to do something that makes them uncomfortable, particularly when it is not vital to their work, is unprofessional.
Bullying a staff member to take a client to a strip club is just plain wrong. As well as the strong possibility that OMG PR will find itself in an employment tribunal, the manager is breaking the CIPR Code of Conduct.
Under the code, professionals are expected to maintain the highest standards of personal integrity and
conduct, to deal fairly with employees and do nothing that might bring the profession into disrepute.
Going to a strip club is not wrong in itself, even if it does potentially exclude female staff from both companies. How you go about it will damage your professional standing if it puts people in a difficult position. The code supplements your own common sense.
Don’t get caught out: check before you act.