BRATISLAVA (Reuters) - Slovakia has banned companies with undisclosed ownership from doing business with the state as part of a package of anti-corruption measures, the justice minister said on Wednesday.

The central European nation, which ranked 50th among 168 countries in Transparency International's 2015 corruption perception index, last year introduced a register of final beneficiaries of companies participating in public procurement.

However, law experts have criticized the measures as not being strict enough to prevent corruption, which analysts say stifles the proper functioning of the state and business environment.

"The state will make business only with companies that will disclose their ownership including their final beneficiary, or a real owner," justice minister Lucia Zitnanska told reporters after the ban was approved by parliament.

The move to withhold government contracts from companies with opaque ownership structures comes as governments across Europe seek to improve corporate transparency and crack down on tax avoidance.

In 2011 Slovakia introduced a requirement to put all public contracts on the internet, which analysts said has led to a drop in prices the government pays for procured services.

The government has also introduced a 35 percent tax on dividends from companies based in countries that have not signed an agreement on the international exchange of tax-related information.

(Reporting By Tatiana Jancarikova; Editing by David Goodman)