A Progressive Conservative MLA in Alberta has resigned from caucus after being arrested during a prostitution sting in the United States when he allegedly tried to solicit sexual services through a classified advertising website.

Mike Allen, who now represents a riding in Fort McMurray as an Independent, was arrested in St. Paul, Minn., on Monday. He was in the U.S. Midwest as part of an Alberta government contingent to drum up trade. Police allege Mr. Allen used the website backpage.com to engage in prostitution, prompting him to resign from government caucus Tuesday.

"He agreed to meet some undercover officers – of course, unbeknownst to him, they were officers – and agreed to meet them and exchange cash for sexual services," police spokesman Howie Padilla said. "He would have been the john in this situation."

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The two undercover officers were women. Mr. Allen was arrested by the human trafficking unit, and he was taken into custody and booked into the Ramsey County Jail.

"He was booked into the jail on suspicion of engaging in prostitution which, in Minnesota, is called a gross misdemeanour," Mr. Padilla said.

Mr. Allen was released on Tuesday. He has not been charged, but police said the investigation is continuing. He was not targeted, Mr. Padilla said, noting it was part of a regular sting operation. Thirteen people were arrested Monday.

The first-term backbench MLA for Fort McMurray-Wood Buffalo released a statement saying "pending resolution of this incident," he resigned from the government caucus and legislative committees. Mr. Allen said he informed the government whip he was involved in a "legal incident."

"I made this mistake as a result of a profound lapse in my personal judgment," he said in a statement on his MLA letterhead, released through the government whip. "It is a mistake for which there are no excuses and for which I accept full responsibility.

"This is a deeply embarrassing moment," the statement said, as he apologized to everyone from his family to "all Albertans" and asked for forgiveness.

Mr. Allen was in St. Paul as part of an Alberta delegation meeting with U.S. legislators at the annual Midwestern Legislative Conference. His job was to discuss "cross-border trade, movements of goods and upgrades of gateways within the region," according a previous Alberta government news release.

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Official Opposition and Wildrose Party Leader Danielle Smith called for Mr. Allen to resign from the legislature. "For an MLA to behave in this manner while travelling abroad on government business is unacceptable," she said in a statement.

Alberta Premier Alison Redford's office declined comment on the allegations against Mr. Allen.

Mr. Allen and his family moved to Fort McMurray 20 years ago, where he purchased Campbell's Music and "was able to combine his business administration background and career as a professional jazz musician to create a successful and thriving business," according to his official legislature biography. He served two terms as president of Fort McMurray's Chamber of Commerce.

Government Caucus Whip Steve Young said while it's important to respect the principle of innocence before being proven guilty, Albertans expect the highest ethical and moral standards.

"I don't care if he was there on a fishing trip … standards are a concern. You're an MLA."

Editor's Note: In an earlier online version of this story, the headline stated that Mike Allen resigned from his role as Alberta MLA. The headline has been corrected to state his resignation from Progressive Conservative caucus.