Redford says Mike Allen's conduct was "more than inappropriate" when he was attending a legislative conference in St. Paul, Minn.
Allen was arrested Monday night by police and faces a possible charge of soliciting a prostitute.
"You'll know that in Alberta when I was justice minister, we started doing work with respect to the sexual exploitation of women and human trafficking. This is an issue that is very close to my heart," Redford told reporters Thursday morning at her annual K-Days breakfast in Edmonton.
"I was shocked and disappointed to see the conduct. It's not at all the standard of conduct I would expect from anyone in our caucus."
Allen has resigned from the governing Progressive Conservative caucus, but he remains as an Independent MLA for Fort McMurray-Wood Buffalo.
Redford says it's up to people in Allen's riding to decide whether he should continue to represent them.
"He's an elected member of caucus. He's an elected person from Fort McMurray. I understand he has said that he will go back to his community, his constituents, to have that discussion. That is appropriate at this time," Redford said.
"He is an individual who will take responsibility for his actions," she added. "He will live with the consequences of his decisions."
During the breakfast, Redford stood on a stage flanked by caucus members who also helped flip and serve pancakes. Allen was nowhere to be seen. The 51-year-old flew to Edmonton from St. Paul on Tuesday night.
Officers there had posted a fake ad on an online site for escorts and massage services called backpage.com. Police spokesman Sgt. Paul Paulos said Allen responded to the ad over the Internet and information was exchanged through cellphone texts about when and where he would meet two female undercover officers.
Allen met the pair and agreed to pay about $200 for a threesome, Paulos said. A team of officers then quickly placed him under arrest.
Redford said she demanded that Allen reimburse the government for all the expenses he incurred on the trip and she said it is her understanding that he has done so.
Opposition parties were swift to condemn Allen after the news broke of his arrest late Tuesday. The official Opposition Wildrose party called for his resignation.
Redford, however, made no official comment until Thursday, and she defended her decision to stay away from reporters' microphones.
"Opposition parties can have their say, or they can do what we did, which is to actually take action. This man has been expelled from caucus, we have insisted that he repay the expenses. We've made it very clear with respect to our position on this and my position on this," Redford said.
"Quite frankly, this is not a race to the bottom to see who can get to your deadlines first," she told reporters. "It's about dealing with the circumstances and making sure that we're taking the time to understand exactly what is going on."
It is expected that Allen will find out by the end of the week whether he will have to return south of the border to face a charge of soliciting prostitutes.
After he was released Tuesday, he phoned in his resignation from caucus and issued an apology for "an embarrassing moment" and "lapse of personal judgment."
Redford said she has not spoken with Allen since his arrest.
Allen was elected as a first-term MLA in last year's provincial election. He had spent two terms as a city councillor in Fort McMurray before jumping into provincial politics.
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