2011, Kosor was elected Deputy Speaker of the Croatian Parliament and was also chairwoman of the HDZ's Deputy Club and leader of the opposition. Kosor contested 2012 HDZ leadership election and came in third out of five candidates. A moderate conservative, Kosor continuously publicly criticized Tomislav Karamarko's leadership and the new, more conservative, party platform. In 2012, she testified at the trial in the Fimi Media corruption case against Ivo Sanader. On 12 June 2012, Kosor and Vladimir Šeks were removed from the positions of Deputy Speakers. In 2013, she was expelled from HDZ for "damaging the reputation of the party". Kosor continued as an independent, considerably more liberal, politician and eventually formed a deputy club with two Croatian Civic Party MPs. Kosor voted in favour of presenting the issue of the 2013 referendum on banning same-sex marriage before the Constitutional Court, and against the proposed Constitutional change which represented a change from her previous position on homosexuality and same-sex marriage since she had been known for being against the expansion of LGBT rights. She also voted for the Life Partnership Act which gave same-sex couples in Croatia rights equal to heterosexual married couples. After receiving death threats in 2015, Kosor was granted police protection. After speculation that she might be the SDP's candidate, Kosor eventually decided to participate in the 2015 parliamentary election as a candidate for the liberal Successful Croatia coalition in the 5th electoral district. She wasn't elected to the parliament. She continued to criticize Tomislav Karamarko and Kolinda Grabar-Kitarović as well as Bridge of Independent Lists party for their indecisiveness. In February 2016, she called on Prime Minister Tihomir Orešković to remove Zlatko Hasanbegović from the position of the Minister of Culture after photograph of him wearing a cap with an Ustaše badge was published. In August 2016, Kosor stated that yelling Za dom spremni was "an insult to war veterans and their friends who gave their lives for a democratic, independent, and free Croatia". Kosor is very active on Twitter where she writes on daily events and statements by politicians. She also maintains a personal blog - "Day After Yesterday - On Obverses and Reverses of Politics". In 2017, she published a book which included texts she wrote on her blog and columns written for the Slovenian leftist newspaper Dnevnik in the period from 2015 to 2017 in which she commented on Croatian interior and