FILE - Tunisian President Kais Saied gives a speech at the new government s swearing-in ceremony at the Carthage Palace outside the capital Tunis, on Feb. 27, 2020. AP
Legislators from the parliament's foreign affairs committee were due to head to the North African country on Thursday on a fact-finding mission.
But in a letter seen by AFP, Tunisia's foreign ministry said on Thursday that the lawmakers would not be allowed entry due to "multiple reservations" about the visit.
"It is both astonishing and exceptional," MEP Mounir Satouri, a member of the delegation, told AFP.
"Never in at least 20 years has a regime allowed itself to refuse an official delegation from the foreign affairs committee and to say that even if we made the trip we would be turned back at the border."
The incident comes after the European Union inked a memorandum of understanding in July with Tunisia aimed at curbing irregular migration across the Mediterranean.
Under the deal -- pushed strongly by EU member Italy -- Brussels has promised potentially hundreds of millions of euros in financial support for the government in Tunis.
Tunisia is a main launching pad for thousands of migrants seeking to make the perilous sea crossing to Europe.
In a debate this week, MEPs on the left complained the EU had struck a deal with an increasingly authoritarian government, which has been accused of abusing migrants from sub-Saharan Africa.
"This memorandum must be revised as it fails to address all concerns related to human rights, including the rights of migrants and asylum seekers, as well as the continued deterioration and deepening of the crackdown on opposition," the socialist S&D grouping said.
But the European Commission, the EU's executive arm, in parliament defended the agreement, saying it reinforced cooperation with a key partner.
International rights organisations have warned over the past two years of a steady slide towards authoritarianism in Tunisia ever since President Kais Saied staged a power grab on July 25, 2021.