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Bulgaria says it will use its six months at the helm of the European Union to soothe tempers between EU headquarters and Poland.

The EU's executive Commission has started proceedings against Warsaw which may eventually lead to a scrapping of its voting rights — if all other EU nations agree.

But Bulgarian Prime Minister Boyko Borissov said Thursday such a vote would be bad for all.

"We should not get to this," Borissov told reporters, adding that "if we get to vote then we will have to have sleepless nights."

Poland last month completed a sweeping overhaul of its justice system, ignoring EU warnings it breached democratic principles and could lead to unprecedented sanctions.