The Dáil has heard that a US-based academic experienced a "sinister and chilling experience" in an Irish airport last week.
Solidarity/People Before Profit TD Ruth Coppinger told the Dáil that the academic, Catherine Kelly, was "stopped at the airport by two plain clothes gardaí."
She said that Ms Kelly was asked for her name, asked if she used social media and "if she had written an article about Minister Regina Doherty and her business dealings."
Ms Coppinger said: "That a complaint could have been made and she was cautioned not to tweet Minister Doherty and any material relating to her."
She added: "She was told to sign a statement. Her name was obviously given by an airline to the gardaí. She was told to sign a statement or she would not be allowed to proceed to the gate."
She said that Ms Kelly "merely raised issues about the minister's dealings in a bankrupt company in 2009.
"We've heard a lot about social media this week. Is it now Government policy to attack anybody who crticises anyone in the Government on social media in this very sinister way, in a very legitimate article that raised questions?"
Speaking on RTÉ's Prime Time, Taoiseach Leo Varadkar said he did not know the facts of the case and had not had an opportunity of discussing the matter with Ms Doherty.
However, he said he believed that gardaí do not caution people over inter-personal disputes or a civil offence.
