"We definitely messed up, but it's much more important what the result of the audit will be. It has always been perfect so far and I believe that it will be so this year as well," Milanovic told the press in Petrinja, about 70 kilometres southeast of Zagreb, where he visited an army barracks.

He explained that the report was late because the party's chief accountant had fallen ill and had to undergo surgery. She returned to work a few days later, but failed to complete the report on time.

"I apologise to our voters and to all citizens who believe and know that the SDP is a transparent party with transparent accounts," he said.

Milanovic confirmed that the State Audit Office was right to deny the SDP's statement that it had granted the party's request for extension of the deadline for the publication of the financial report. "It was a misunderstanding. They immediately denied our incorrect information, which best shows that this office ... was under no pressure," he added.

Responding to a reporter's remark that the SDP was now facing a fine of 5 million kuna, Milanovic said that it was not a fine but an administrative suspension of a considerable amount of funding, which he said was imposed in "drastic circumstances". He said that if the SDP were in court, it would be granted a grace on account of an emergency situation, but added that the party would not insist on it.

"We don't know what is done in such situations because we haven't had such problems before," Milanovic said, noting that the law that regulates the financing of political parties is illogical in some parts because penalties for certain omissions are too low while for some they are "absolutely draconic".