Former European Council President Donald Tusk was unphased by Monday’s news that the prosecutor’s office had launched an investigation against him, suggesting the complainant may have acted under the influence of Moscow, writes euractiv.com.

The investigation was launched after a complaint by businessman Marek Falenta, who alleged that Tusk, who served as prime minister between 2007 and 2014, abused his powers to order an inspection of the company, Składy Węgla (Coal Stocks), that he ran and which was involved in importing Russian coal to Poland.

The Law and Justice (PiS) party “persecutes me for my fight against Russian coal import. The prosecutor’s office acts for the request of Marek Falenta, an importer of this coal, convicted of illegal wiretapping,” Tusk tweeted on Tuesday.

“A scenario written with the Cyrillic script”, Tusk added in his tweet, suggesting that Falenta may have had ties with the Kremlin.

Falenta made secret recordings of leading politicians, including later EU Commissioner Elżbieta Bieńkowska, then foreign minister Radosław Sikorski and bank owner Mateusz Morawiecki, now Poland’s prime minister. The tapes came to light in 2014 and helped bring down the government of Tusk’s Civic Platform (PO) party in 2015, less than a year after Tusk assumed his post as European Council president.

Tusk believes that it was the PiS party, a long-running adversary that cooperated with Falenta to oust the PO cabinet. In a letter dated 11 April but first reported by TVP on Monday, prosecutors confirmed the opening of an investigation into whether Tusk abused his powers by ordering a review in Falenta’s company. Falenta accuses Tusk of “ordering without legal basis an inspection of the firm Składy Węgla with the aim of forcing the cessation of coal imports from the Russian Federation and thus acting to the detriment of the company’s private interests,” as stated in the prosecutors’ letter. The crime carries a potential prison sentence of up to ten years.

The investigation’s result may also influence the general election later this year, with PiS attempting to deprive Tusk, now again PO’s leader, of the possibility to exercise public functions.