Interior Ministry data shows that the initiative by a group of NGOs and individuals was only signed by 2,151 people, short of the 2,500 signatures needed to initiate proceedings for a referendum, according to Virant.

"The initiative is thus invalid and the law will be promulgated. I have already signed the act and sent it to the president's office. It will be promulgated, published in the Official Gazette and take effect," the speaker of the National Assembly told reporters.

If the initiative, filed two days ago by the group dubbed "Let's Stop TEŠ6", was valid, the speaker would have to set a period in which the group would need to collect 40,000 signatures to call the vote.

TEŠ welcomed the news of the failed referendum initiative, announcing that the construction of generator 6 and activities for the drawing of finances could and now proceed unhindered.

"This will ensure a high rate of [Slovenia's] self-sufficiency in energy supply also in the future," TEŠ said in a statement for the STA.

The law that the National Assembly passed last week approves a state guarantee for a EUR 440m loan from the European Investment Bank on condition that the price tag on the project does not exceed the current EUR 1.3bn.

TEŠ will also have to revise the investment plan and have it approved by an independent auditor as well as by the supervisors of TEŠ and its owner HSE before it can get the guarantee.