In a post on his Facebook profile posted on Saturday, Janša stressed Šarec's appointment was enabled by the Left, "an extremist left party whose ideal is the Venezuelan socio-political system".
He said the party advocated "higher taxes, nationalisation of private property, Slovenia's withdrawal from NATO" in addition to "opposing the sale of the state-owned NLB bank requested by the European Commission".
The leader of the election-winning SDS moreover rebuked Šarec for having "no experience in state politics", going as far as saying that he "doesn't even know the difference between the Council of the European Union and the Council of Europe".
He said Šarec was known in Slovenia as an impersonator and "cheap entertainer" who had built his popularity on sophomoric humour which often crosses into insults, mostly about women.
Janša also reiterated the SDS had won more votes in the 3 June election than the second and third-ranked parties together. What is more, it received more votes than all three parties that form the outgoing Miro Cerar government (the SMC, SD, DeSUS), which are now re-entering an almost identical government coalition.
Janša believes that "such fierce exclusion of the election winner", the appointment of the prime minister-designate and the new coalition's line-up are a consequences of the still very strong forces rooted in the former communist regime and its secret police, which are assisted by "the regime media".
The SDS leader also said that these "influential" forces have the power to "turn the absolute defeat in the parliamentary elections into a position where they still maintain their power and provide for their privileges".
Janša said it is still not clear whether the Left, which has signed a cooperation deal with Šarec's coalition, will vote for Šarec's government or abstain from voting.
"In this case, Slovenia could face a new early election", he concluded his post written in English and entitled A New Extreme Left Government Possible in Slovenia.