Bulgarian Prime Minister Boyko Borisov has blamed UNESCO Director-General Irina Bokova for sabotaging the candidacy of Kristalina Georgieva for the office of UN Secretary General.

The Prime Minister, commenting the UN Security Council vote results for the first time since the last straw poll was held on Wednesday, has also refused to step down, amid calls from the opposition to do so.

Bokova, whose UN candidacy was dropped by the government at the end of September but refused to leave the race after being replaced by EU Commission Vice President Kristalina Georgieva, should have stepped down, he has suggested.

Borisov has fended off comments that that the government should feel "ashamed" after the results, which saw Bokova come second in terms of support after the sixth straw poll, with Georgieva being near the bottom of the ranking and former Portuguese PM Ant?nio Guterres being proposed as next UN chief.

"Ashamed of what? Of not having secured a five-year term for a communist family?" he has asked rhetorically, in a briefing with reporters.

Bokova's critics have repeatedly slammed her candidacy due to her "communist" ancestry, her father having been the editor-in-chief of the communist mouthpiece.

"Who has seen Ms Bokova in Bulgaria for the past 20 years? And how will this [her hypothetical victory in the race] affect the Bulgarian [people]?"

If someone demands Borisov's resignation over the development, this is what all prime ministers of states whose candidates should also do, he has added.

Nominating Georgieva in the eleventh hour was no mistake, since "we had the assurances of many countries they would back her," Borisov has added.