The opposition parties base their motion on the dealings of a company owned by the minister, after media discovered that Omerzel's firm Lastinski was planning to extend its contract with the state-owned motorway company DARS despite Omerzel's claims it would terminate cooperation.

SDS deputy group leader Matjaž Tanko told the press on Tuesday that another reason for the motion was Omerzel's failure to appoint a new boss of the Mapping and Surveying Authority, which has been headed by an acting director.

Moreover, the SDS said Omerzel failed to report on the construction of a new generator at the TEŠ coal-fired power plant. Meanwhile, the price tag on the EUR 1.4bn project seems to be increasing once again, said Tanko.

The third opposition party, the People's Party (SLS), was not invited to contribute the signatures for the motion but said it would vote in favour.

Omerzel was widely believed to be on the chopping block anyway, but he said after Friday's meeting with the prime minister that he would stay on. His party, the Citizens' List (DL), continues to support him as well.

However, it is not clear whether all coalition parties would support him. He was supposed to meet with coalition deputy groups on Monday and Tuesday but no meeting has taken place.

Omerzel is however confident that he will stay on as minister, saying yesterday that he did "not fear the interpellation motion at all". He will however comment on the motion after he reads it.

The opposition has already unsuccessfully mounted a challenge against Finance Minister Uroš Čufer and the second interpellation motion, against Interior Minister Gregor Virant, is scheduled for vote later this week.