The Welsh Assembly Standards Commissioner has resigned after accusing Neil McEvoy of ''illegally'' recording confidential conversations between him and his staff.
Sir Roderick Evans said the Assembly Member's behaviour ''undermines the integrity of the complaints procedure'' in his resignation letter on Monday evening.
McEvoy, who secretly recorded Sir Roderick, said he believed the recordings were in the public interest.
He alleged he had found evidence that brought Sir Roderick's office into disrepute.
Sir Roderick said: ''It has come to my attention that conversations with my staff about a variety of highly confidential and sensitive matters have been secretly, and possibly illegally, recorded over a period of what seems to be several months and in what seems to be a number of different locations by an Assembly member.
''These have included highly confidential conversations with my staff, including references to cases brought by members of the public.
''When considering and investigating complaints it is necessary for me and my staff to have open and frank discussions about the complaints, the appropriate approach to them, and their implications.
''Much of what has been shared by the media has been taken out of context and is misleading.
''That a member of our National Assembly could behave in this way is wholly unacceptable.
''It undermines the integrity of the complaints procedure and brings out democratic process into disrepute.
''I'm not prepared to continue in my roles as Standards Commissioner.''
Speaking to the BBC, presiding officer Elin Jones said she will be ''asking South Wales Police to investigate how such recordings were obtained''
At a press conference on Tuesday, McEvoy described her plans to sweep the Assembly for recording equipment as ''ridiculous.''