WARSAW, April 11 (Reuters) - Polish special services are investigating if Orlen Trading Switzerland, a unit of Polish refiner Orlen, breached sanctions on the import of oil from Russia or Iran, private broadcaster Radio Zet reported on Thursday.

The investigation would be the latest probe to target the state-controlled company, after prosecutors started examining whether it artificially lowered prices ahead of a 2023 election, creating losses, and sold assets at prices at below their fair value to acquire a smaller peer, Lotos.

Orlen did not breach any sanctions, the company said in an emailed response to Reuters' questions on Thursday.

The current government says the previous nationalist Law and Justice (PiS) administration had exerted political influence over state-controlled companies.

Radio Zet's report came after Orlen said on Wednesday a 1.6 billion zloty ($403.82 million) write-down of the value of Orlen Trading Switzerland (OTS) would decrease the group's 2023 profit.

The trading unit has prepayed purchases of oil and refining products but did not receive the products by the agreed deadline. The reimbursement of the prepayments has been assessed by OTS as unlikely, Orlen said.

"Contrary to standards, the advance payments were paid without collateral to entities with which Orlen had never cooperated before," the company said on Thursday.

Orlen Trading Switzerland was set up in Zug in 2022 ahead of the European Union ban on imports on Russian oil products that came into force in early 2023.

A spokesman for the coordinator of special services did not immediately reply to email and phone requests seeking comment.

Poland's Internal Security Agency (ABW) and the Central Anti-Corruption Bureau (CBA) did not immediately respond to emailed requests for comment.

"I did not have any information about this case during my term of office. The secret services also never informed me of any irregularities or concerns in this regard," Jacek Sasin, a former PiS minister in charge of state assets said in an e-mailed statement. (Reporting by Marek Strzelecki, Anna Koper, Alan Charlish; editing by David Evans and Ros Russell)