Pringle was elected as a Teachta Dála for the Donegal South-West constituency at the 2011 general election, unseating the incumbent TánaisteMary Coughlan. He quickly became an ally of Luke 'Ming' Flanagan, elected as an independent TD at the same time as Pringle, but for the Roscommon–South Leitrim constituency. Flanagan and Pringle would go on to support each other on many issues, including reform of the Common Agricultural Policy and opposition to the MERCOSUR deal. Even when Flanagan was elected as a Member of the European Parliament for the Midlands–North-West constituency after spending three years in the Dáil, himself and Pringle continued to work together, and Flanagan visited Donegal specially to canvass for Pringle ahead of the 2020 general election. On 5 December 2011, Pringle delivered a televised address to the nation, representing the technical group of TDs in Dáil Éireann. He did so in response to Taoiseach Enda Kenny's Address to the nation of the previous evening. Later that month, Pringle called on people for support in a campaign not to pay a new household charge brought in as part of the latest austerity budget, and announced that he would not register for the tax or pay it. In February 2012, he published his expenses online. He was elected leader of the Technical group in Dáil Éireann in March 2012. In May 2012, Pringle brought an unsuccessful High Court challenge over the 2012 European Fiscal Compact referendum. and the ESM Treaty which was appealed to the Supreme Court in July 2012. In July 2012, the Irish Supreme Court decided to refer three questions to the Court of Justice of the European Union arising out of his challenge to the European Stability Mechanism Treaty and doubts about the legality under the European treaties of the ESM. The CJEU held an oral hearing on the referral on 23 October 2012. The full court of 27 members sat in an historic sitting, it was the first time that the full court sat to hear a reference from a member state of the union and heard oral arguments from counsel for Pringle, Ireland, nine member states, the commission, the council, and the European Parliament. On 27 November 2012, the EU Court of Justice dismissed all arguments of Thomas Pringle. In the 2016 general election, after a re-drawing of constituency boundaries, Pringle campaigned in the new five-seater Donegal constituency. He was re-elected to the final seat by a margin of just 184 votes over Sinn Féin's Pádraig Mac Lochlainn. During negotiations to form a government, Pringle said he was glad not to have signed up to the Independent Alliance, after that group entered talks with Taoiseach Enda Kenny. Pringle said that unless Kenny or Fianna Fáil leaderMicheál Martin signed up to Right2Change, he would not support either as Taoiseach. As of April 2016, Pringle had become a member of the Independents 4 Change technical group in the Dáil. In May 2016, Pringle introduced legislation designed to retain water in public ownership and avoid further privatisation. Pringle is also credited with stopping the Irish state from investing in fossil fuels.
