The EU competition enforcer typically uses a statement of objections to list specific areas where mergers could result in higher prices or put pressure on rivals, which can spur the company making the takeover bid to offer concessions.

"The Commission confirms that it has sent a Statement of Objections to PKN Orlen in the context of the assessment of PKN Orlen's proposed transaction of Lotos. The investigation is ongoing," the Commission said, adding that the provisional deadline for it to take a decision is June 30.

The state-run PKN Orlen said that this is a regular procedure and that it would soon present its concessions on the planned deal.

"We are determined to complete the transaction. The current situation on the fuel and energy markets shows that companies have to diversify operations, as it increases their resilience to macroeconomic fluctuations and the geopolitical situation," PKN Orlen CEO said in a statement.

PKN Orlen announced in 2018 that it planned to buy at least 53% of Lotos. In August last year the Commission opened a full-scale investigation into the deal, saying it might lead to higher prices and restrict competition.

The deal has triggered concerns from rival BP, which has 575 Polish petrol stations compared with PKN's 1,800 and the 506 owned by Lotos, in which Poland holds a 53.19% stake.

(Reporting by Agnieszka Barteczko; Additional reporting by Foo Yun Chee in Brussels; Editing by Alexandra Hudson and Jane Merriman)