An AM is being investigated by the assembly's standards commissioner over allegations he misused assembly funds, BBC Wales understands.
Independent AM Neil McEvoy is accused of printing party political leaflets using assembly resources and employing assembly staff for campaigning.
Staff and resources are only to be used by AMs for work as assembly members.
Mr McEvoy said the "establishment" was reacting to "difficult questions" he asked and he would keep asking them.
The complaints against South Wales Central region AM Mr McEvoy, who is also a Cardiff councillor, have been made by his former office manager, Michael Deem, who was sacked by Mr McEvoy in March.
Both men are expected to give evidence to the investigation.
BBC Wales understands that the allegations against Mr McEvoy include that he:
- employed permanent and temporary members of staff for the purpose of campaigning
- used his assembly funded office for political and campaigning purposes
- printed party political leaflets on a photocopier provided by the Assembly Commission (responsible for the day-to-day running of the institution)
- charged the cost of this printing to his office cost allowance
- used audio/visual equipment purchased through the Assembly Commission to produce candidate campaign videos
- using the assembly ICT (or IT) systems to perform political/campaigning tasks.
Responding to the allegations, Mr McEvoy said: "When you take on the establishment, the establishment bites back.
"I will continue to ask the difficult questions that some people don't want asked. I will continue to do not politics as usual."
The BBC has been told the hearings started in November and there have been five sessions so far.
When concerns are raised about the conduct of assembly members, they are investigated by the standards commissioner.
Sir Roderick Evans is an independent person appointed by the assembly to safeguard standards, to uphold reputations, and to address concerns.
He refused to comment.
The code of conduct for assembly members sets out how AMs can use the allowance they are given to do their job, and what is not allowed.
It states: "Assembly members must ensure that they use assembly resources for the purpose of their activities as assembly members only and not for any of the purposes listed below, which are prohibited."
- personal, business or commercial communications
- party political activity of any kind, for example, party-political fund-raising, recruitment of party members and the organisation and publicising of party political meetings
- campaigning for the election or re-election of particular candidates for any public office (including the member in question)
Mr Deem declined to comment.