Ljubljana - The Left and New Slovenia (NSi) have clashed over the opposition party's proposal to tax empty and large properties in a major election campaign issue that pits the two parties on the opposite sides of the ideological divide.

Faced by criticism from the junior coalition partner, which is seeking a referendum on the issue, the Left amended its original proposal to increase the size of properties that would be subject to extra tax.

Luka Mesec, the leader of the Left, says the aim of their bill is to tax the owners of empty properties and those who have amassed real estate to create a systemic source to build 30,000 public rental homes.

In a bid to tackle acute shortage of affordable housing, the party initially proposed imposing extra tax on properties larger than 120 sq meters of residential surface except when owners or their family members live in them permanently.

The party has now increased the threshold to 160 square metres with Mesec saying today they were "willing to discuss whether this figure is suitable for flats and houses, we're willing to talk about what the suitable surface area is".

Since the NSi will not hear it but prefers to "stick up posters saying the Left will tax you houses on Slovenia's periphery", Mesec said the Left opted to table a new proposal.

He assured the public that "none who don't pay tax today will pay it under the proposal".

The NSi has submitted a proposal to call a consultative referendum on the proposal. NSi deputy group leader Jožef Horvat said as far his discussions with coalition partners and "allies" show support for the proposal is secured.

The issue is about what life is Slovenia will be like: "Whether we want higher taxes and a big state that will distribute the funds as advocated by the Left or do we want lower taxes so people earn more from their work, which is what the NSi advocates. People should decide on that in a referendum," said Horvat.

Speaking before the Left amended its proposal, he said the proposed tax would "additionally increase taxation of properties, including those people use themselves or live in them with their families and are larger than 120 sq metres".

He called the proposal an "attack on the Slovenian countryside where people in the past built large houses [...] for themselves and for their son or daughter and their family".

"The shortage of homes is not in the countryside, it's in urban centres [...] The Left's proposal means people in the countryside are second-rate citizens," said Horvat, adding that being from Prekmurje the proposal hurt him.

He wondered whether "we are on the doorstep of a new nationalisation the prospect of which the Left has been announcing for a while".

Commenting on the proposal to raise the tax rate on rented flats by 50%, Horvat said the tax would be paid directly by the tenants. Instead, he proposed tax incentives for investors to stimulate housing construction.