The Tunisian authorities have denied entry to five members of the European Parliament's foreign affairs (AFET) committee, who were due to start an official mission to the country on Thursday.
In a letter addressed to the European Union's delegation in Tunis, Tunisia's foreign affairs ministry said that the parliament's delegation would "not be authorised to enter national territory."
The parliament's foreign affairs committee has condemned the Tunisian authorities' decision and demanded a "detailed explanation."
"This conduct is unprecedented since the democratic revolution in 2011," the committee said in a statement.
A spokesperson on behalf of the European Commission said on Thursday that the Tunisian government's decision "came as a surprise to us," but could not confirm whether it would impact the controversial migration agreement the EU recently signed with Tunisia.
The delegation's visit intended to evaluate the current political situation in Tunisia after its fact-finding mission in April this year found "political backsliding on democratic standards and human rights" in the country.
It was also due to assess the EU-Tunisia migration deal. The five MEPs were set to meet with NGOs, trade unions and opposition leaders, but had failed to secure meetings with the Tunisian government.
The members of the European Parliament (MEPs) due to travel to Tunisia were Germany's Michael Gahler of the European People's Party (EPP) and Dietmar Köster of the Socialists and Democrats, and French MEPs Salima Yenbou of Renew Europe, Mounir Satouri of the Greens and Emmanuel Maurel of The Left.
Speaking in Strasbourg on Thursday, Gahler, the delegation lead, said that they should have left for Tunis that very day and arrived by evening.
The move follows a heated debate in the European Parliament's plenary session on Tuesday where lawmakers criticised the EU's controversial migration pact with Tunisia.
During the debate, Satouri, one of the MEPs due to travel on the mission, said that the EU's actions meant it was "being held hostage by authoritarian regimes."
"Every time you give up border management to dictators, you are making us vulnerable," he said.
MEPs have consistently criticised the EU-Tunisia deal for failing to recognise mounting evidence of Tunisian authorities’ abusive treatment of sub-Saharan migrants, including illegal pushbacks, racial hatred and human rights violations.
They have also criticised the European Commission for cosying up to Tunisia's President Kaïs Saïed, who has embraced far-right conspiracies that migrants are plotting to change the country’s demographic make-up.