Hungarian former government insider-turned critic Peter Magyar on Thursday said he has been put under investigation by a controversial new government agency set up to curb foreign influence.
The Sovereignty Protection Office began operating in February with critics fearing it would have a "chilling effect" on the country's democracy.
The office has powers to "identify and investigate organisations that receive funding from abroad aimed at influencing the will of voters".
"The latest news is that the so-called Sovereignty Protection Office has opened an investigation against me for attempted foreign influence," Magyar wrote on Facebook.
Magyar shot to prominence in Hungarian politics after unprecedented anger erupted against the long-ruling government of nationalist Prime Minister Viktor Orban over a child abuse scandal.
The Sovereignty Protection Office said it was launching an investigation "into information published in the Hungarian press that raises suspicions of a foreign financing attempt," news agency MTI reported.
The office cited a suspicion that "the same interest group and network of foreign and Hungarian actors" that supported Orban's challenger in the last parliamentary elections in 2022 is now "targeting" the Hungarian elections again.
The office did not immediately return AFP's request for comment.
A lawyer and former insider, Magyar, 43, has formed his own political party to run in European and local elections in June and challenge the party of Orban, who has ruled the central European country of 9.6 million since 2010.
Recent rallies held by Magyar, the ex-husband of Orban's former justice minister, have drawn tens of thousands of people in Budapest.
Orban is facing the biggest political crisis of his 14-year premiership since it emerged in February that a man convicted in a child sex abuse case had been granted a presidential pardon and was released from jail.
Since returning to lead the EU member state, Orban has moved to curb press freedom and made other changes to tighten his grip on power, often clashing with Brussels over rule-of-law issues.
Last month, Europe's top rights watchdog, the Venice Commission, called for the Sovereignty Protection Office to be scrapped, saying it wields disproportionate power.
The European Commission launched infringement proceedings against Hungary, while the United States has also expressed "concern" over the issue.
The Sovereignty Protection Office has broad powers to gather information, cooperate with state agencies and make reports.
While it does not have the power to sanction anyone on its own, under Hungarian law any candidate standing for election that accepts foreign funding could face up to three years in prison.
