UN nuclear watchdog International Atomic Energy Agency (IAEA) chief Rafael Grossi on Saturday condemned Iran’s “disproportionate and unprecedented” move to bar multiple inspectors assigned to the country, hindering its oversight of Tehran’s atomic activities.

“I strongly condemn this disproportionate and unprecedented unilateral measure which affects the normal planning and conduct of agency verification activities in Iran and openly contradicts the cooperation that should exist between the agency and Iran,” Grossi said in a statement.

Iran’s move, known as “de-designation” of inspectors, is allowed; member states can generally veto inspectors assigned to visit their nuclear facilities under the Nuclear Non-Proliferation Treaty (NPT) and each country’s safeguards agreement with the agency governing inspections. But the IAEA said Tehran’s decision went beyond normal practice. It said Iran had told it that it would bar “several” inspectors, without giving a number.

“These inspectors are among the most experienced agency experts with unique knowledge in enrichment technology,” the agency said. “With today’s decision, Iran has effectively removed about one-third of the core group of the Agency’s most experienced inspectors designated for Iran.”

Iran defended its move and accused the United States, Britain, France, and Germany of politicising the IAEA watchdog. “Unfortunately, despite Iran’s positive, constructive and continuous interaction of the with the agency, the three European countries and the United States abused the (IAEA’s) Board of Governors for their own political purposes,” Foreign Ministry spokesperson Nasser Kanaani told state media.

“Of course, Iran will continue its positive cooperation within the framework of the agreements that have been made, and emphasise the necessity of the agency’s neutrality,” he added.