"This is no pressure on the judiciary, but what the HDZ did today is more than pressure on the judiciary -- it's a small coup," Milanovic said at a press conference in the Parliament building.

He was commenting on today's decision by Parliament to lift the immunity of SDP MP Jovanovic from prosecution after the ruling Croatian Democratic Union (HDZ) filed a private defamation suit against him for calling its leadership a criminal organisation.

"This is the first time in 20 years that an MP has been stripped of immunity for what they said and with it a verbal offence has been reinstated. Immunity exists so that MPs can speak freely, without fear of consequences, and not to protect them from prosecution for any property-related crimes or homicides they may have committed," Milanovic said.

When asked if the SDP would stand by its announcement that it would take part in voting on five so-called European laws and on the interim budget bill, Milanovic said: "We must discuss it today and we will see."

He was also asked to comment on a letter by the HDZ to the State Election Commission in which the ruling party said that the SDP-led coalition, by displaying election posters in Zagreb, had begun promotional activities before the election campaign officially started.

"I don't see anything unlawful here. There was no mention of any law being violated, which only shows the legal literacy of the authors of the letter," the SDP leader said.

Jovanovic said that today's decision by Parliament was "a shot at parliamentary democracy", adding that it only confirmed once again that the HDZ leadership, headed by Jadranka Kosor, was a criminal organisation and that citizens would make their final judgement on it at December elections.