Independent Cairns MP Rob Pyne has been referred to the state's powerful ethics committee after he signed a man into Parliament who has been charged with stalking another MP.
Speaker Peter Wellington said "further examination of the facts are required" in relation to the matter.
"I take breaches of our security procedures very seriously," he said.
He said there was a "prima facie" case of a security breach.
The ethics committee can recommend to parliament that an MP be expelled.
EARLIER: A Queensland female MP has alleged she was put at risk inside State Parliament after a man charged with stalking her was allowed to enter the building by another MP, in a major security breach.
Speaker Peter Wellington has described the security breach by Cairns MP Rob Pyne as "very grave" and said he will investigate whether he "knowingly" participated in the attempt to "threaten and intimate" Keppel MP Brittany Lauga.
Petros Khalesirad is facing trial for allegedly stalking Mrs Lauga, who is pregnant with her first child and due next month.
Khalesirad is accused of harassing and threatening Mrs Lauga over electronic devices by posting inflammatory comments on social media as well as her address and mobile phone number between February 20 and August 27 last year. His bail conditions state he is not to contact her or approach her home or electorate office.
However he sat in the public gallery watching question time on Tuesday and was signed in by Mr Pyne for a meeting in his office.
Mrs Lauga wrote to the Speaker to alert him to the incident and claimed Mr Pyne could have committed contempt of Parliament.
"Despite having full knowledge of the charges against Mr Khalesirad, the Member for Cairns signed Mr Khalesirad into the parliamentary precinct and took him around the Parliamentary Precinct," she said in the letter.
Mrs Lauga claimed in the letter that she had told Mr Pyne last month that Mr Khalesirad had been charged with unlawful stalking.
Mr Pyne could be referred to the parliament's powerful Ethics Committee as a result of the incident, with Mr Wellington saying the incident put staff and MPs at risk.
He also criticised Mr Pyne for allowing Khalesirad to be in the building unaccompanied.
Mr Pyne admitted signing the man in but said he was not aware of the orders prohibiting him from being in contact with Mrs Lauga.
"I was in my office yesterday and I had not made an appointment with this gentlemen but he rang my office … and asked to come in," he told The Courier-Mail.
Mr Pyne said he was upset and surprised at the Speaker's investigation into the matter and praised Mr Khalesirad's behaviour in his written reply to Mr Wellington, obtained by The Courier-Mail.
"I found his behaviour to be exemplary," he said in the letter.
Mr Pyne made a social media post last month about the case involving Khalesirad and Mrs Lauga. However he said in the letter he did not read the article about the court case before posting it to social media.
Mrs Lauga told the Rockhampton Magistrates Court last month that she was "terrified" and it was a "horrible, horrible experience".
"It brought fear of what he would say next, fear that he was watching me, fear that I was under surveillance," she said.
"There were dozens upon dozens of posts, daily. I feel like my phone is bugged or tapped."
An unrepentant Mr Pyne questioned whether the complaint was politically motivated and said he would not offer an apology until he was satisfied it was genuine.
"If they're using it for political purposes I'm not keen to offer an apology because I don't want to reward bad behaviour," he said.
Khalesirad's trial has been adjourned to December.
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