The changes are designed to crack down on those who cannot explain the origin of their assets.

Under the proposal, the period in which tax authorities can launch proceedings to levy tax on undeclared income will be extended from five to ten years.

If tax inspectors find the person is spending assets substantially exceeding declared income, they would be able to impose a 70% tax on the difference established.

Undeclared income had so far been taxed at the average income tax rate.

"If someone can spend well something they cannot explain where they got from, the state will take what is hers," PM Alenka Bratušek said as she presented the motion in September.

She also announced that the super tax would not discharge the person liable of criminal liability as those procedures were being conducted separately.

The piece of legislation is to take effect on 1 January 2014. Before that, it will undergo the full three readings. The general debate was requested by the opposition Democratic Party (SDS).

Apart from imposing the super tax, the motion also aims to make tax enforcement more effective by including closest relatives among tax debt guarantors. Suspension of statues of limitation is also being proposed.