BRUSSELS (Reuters) – The European Commission said on Wednesday that none of the six European Union countries that do not yet use the euro currency meet the criteria to become member of the euro zone, although Bulgaria was the closest.

Out of the 27 countries that form the EU, Sweden, Poland, the Czech Republic, Bulgaria, Romania and Hungary still use their own currencies rather than the euro, but they are legally obliged to adopt the single currency eventually.

Denmark also still uses its own currency, but it has a legal exemption from adopting the euro.

“None of these Member States currently meets all of the criteria for joining the euro area. Bulgaria is the only country that fulfils all but one criterion and where national legislation can be considered to be compatible with the rules of the Economic and Monetary Union,” the Commission said.

To start using the euro, each of the six countries has to meet criteria of low inflation and borrowing costs, public debt and deficit in line with EU laws and a stable exchange rate.

They also have to have their central bank law compatible with EU law on the European Central Bank to protect central bank independence, prohibit monetary financing and the integrate the national central bank in the European System of Central Banks.