Chris Whitehouse, founder and chairman of The Whitehouse Consultancy was being investigated by the industry body after he published a LinkedIn post (above) that questioned Boris Johnson’s suitability for office.
It said: "Short of dying or publicly losing his sanity, or raping a member of the Royal Family, that means Boris Johnson is heading to 10 Downing Street. Is that good or bad?"
Becca Wright, a public affairs professional who works for a major food manufacturer, shared the post on Twitter after becoming frustrated that no one had criticised the language used in the post.
Wright said: "I think violent language has crept into political discourse over the last few years and has made everyone immune."
A complaint was made by Liam Herbert, chief executive of Helgate Limited and executive committee member of the PRCA Public Affairs Board on 26 June.
"The reasons for my complaint are very clear and I am sure that any reasonable person reading Mr Whitehouse’s comments would agree with my criticism," he said.
Chairman of the Professional Practices Committee, Claire Walker, said: "The PRCA’s Professional Practices Committee held a hearing on the matter on Friday 2 August and delivered their judgement on Monday 12 August.
"An appeal was lodged on Friday 16 August and the PRCA Board of Management considered the appeal and decided to uphold the PPC’s judgement. Chris Whitehouse was issued with a written warning against his use of violent language in his social media post."
Whitehouse did not respond to a request for comment.