Mr Reid and his partner, Alex Barr, who ran Beattie Media's political lobbying section, had been recorded by undercover reporters boasting of their connections with ministers when they were touting for work. Mr Reid told them he was the son of the Secretary of State.
On Thursday, the official Scottish Parliament report into the affair cleared ministers of any wrongdoing in the affair, but commented that there was a conflict of evidence between Mr Barr's submissions and those given by Christina Marshall, secretary to Jack McConnell, the Scottish Finance minister.
Mr Barr had claimed in his evidence that Ms Marshall agreed during a telephone call to an invitation to Mr McConnell from the firm to speak at a financial awards dinner. But Ms Marshall insisted she had not confirmed the engagement.
The report also called for the ministerial code of conduct to be re- examined to tackle public concern over lobbyists.
The report from the Standards Committee of the Scottish Parliament did not specifically examine the behaviour of Mr Reid and his colleagues, which was beyond its remit. However, in their evidence Mr Reid and Mr Barr said their comments had merely been an over- enthusiastic sales pitch.
Kevin Reid's presence in Beattie Media has caused tension between his father and Donald Dewar, Scotland's First Minister. Mr Dewar's decision to order an inquiry into the affair angered John Reid, who felt his son had been persecuted by the press. The report was welcomed by John Reid as vindicating his son.
A spokesman for Beattie Media said Kevin Reid's decision to leave the company was entirely his own.