A report by the EU's executive said on Tuesday that Turkey's bid to join the bloc had “come to a standstill” amid serious democratic shortfalls.
The European Commission said President Recep Tayyip Erdogan's government had overseen a continued erosion of democracy, the rule of law, fundamental rights and the independence of the judiciary, and had ignored the EU's recommendations last year.
“There was further backsliding in many areas,” the commission said. “Under the current circumstances, Turkey's accession negotiations have effectively come to a standstill.”
The report also suggested for the first time that Ankara was no longer serious about delivering on EU-backed reforms.
Turkey clashed with European leaders last year on various issues, including Syria, gas exploration in the Eastern Mediterranean and cartoons of the Prophet Mohammed.
EU leaders agreed in March to provide more money for refugees hosted in Turkey, and in April Mr Erdogan said his country remained committed to obtaining EU membership.
In June, Germany sought to offer a European olive branch to Turkey, telling Ankara that it could send a positive signal to the EU by pulling its troops out of Libya.
Meanwhile, Turkey's foreign ministry said the report showed a “double-standard approach” by the EU and rejected the “unfair criticisms and baseless claims”.
It accused the bloc of failing to keep its promises to Turkey and of not fulfilling its responsibilities.
“Turkey maintains in the strongest terms its strategic choice of full EU membership,” the ministry said.
“It would be in everyone's interest if the EU, taking into account our common general interests, sees Turkey as a candidate country that is negotiating, not as a partner with whom to have daily give-take relations.”
In its 2021 report, the commission questioned Turkey's “ability to assume the obligations of membership” and said Ankara pursued reforms in areas from the economy to rule of law “on a rather ad hoc basis".
It is for the EU's 27 member states, not the commission, to decide whether Turkey's EU membership bid should be formally annulled. Many believe they should nudge Turkey into a different, looser relationship based around deeper trade ties.
A Nato ally, Turkey has been negotiating its EU membership since 2005 after economic and political reforms that made it an important emerging market economy and trade partner.
But since Mr Erdogan's hardline response to an attempted coup in July 2016, the paths of EU and Turkey have diverged sharply, despite better diplomatic relations since the start of 2021.
A purge of opponents that began in mid-2016 continues, the report said, noting “broad-scale restrictions imposed on the activities of journalists, writers, lawyers, academics, human rights defenders and critical voices".
Ankara says its security measures are necessary, given the severity of the threats facing Turkey, which shares land borders with Iraq and Syria.
Mr Erdogan's increase of presidential powers from 2017, which the EU says lack sufficient democratic checks, and his more forceful foreign policy, have also badly strained relations.