A senior figure in Bulgaria's Turkish community lashed out Friday at President Recep Tayyip Erdogan, in a further escalation of a spat ahead of elections in the EU country and a referendum in Turkey.

In a rare outburst, Ahmed Dogan, the long-serving former leader of the main party representing the Turkish minority, said that the Turkish referendum on creating an executive presidency was "madness".

"On April 16 neighbouring Turkey will hold a referendum to turn Kemal (Ataturk's) Republic of Turkey into a sultanate," the 62-year-old said in a statement.

Bulgaria is home to a 700,000-strong ethnic Turkish minority, a legacy of the Ottoman empire.

Turkey, its neighbour, is home to more than 200,000 ethnic Turks with Bulgarian passports who left Bulgaria during the communist era.

Around a third of them are expected to vote in Bulgaria's election on March 26.

Sofia has accused Ankara in recent weeks of meddling in its election, summoning Turkey's ambassador and recalling its own envoy from Turkey for consultations.

Turkey's envoy openly backed Dost, a new party that split from Dogan's Movement for Rights and Freedoms (MRF) in 2016, which is the third biggest in parliament.

Ognyan Gerdzhikov, Bulgaria's interim prime minister, on Friday acknowledged there was a problem.

"There is a certain amount of tension linked to one of the political parties that receives backing from the Turkish side but we are taking measures to stop that," Gerdzhikov said.

It is still unclear how many votes Dost, which unlike the MRF openly backs Erdogan, will garner on March 26 but experts believe it will fail to pass the four-percent threshold to enter parliament.

A wider row is meanwhile raging between Turkey and the European Union ahead of the referendum, with a number of countries preventing Turkish ministers from attending referendum rallies.

An angry response by Ankara has seen German and Dutch politicians called "Nazis" and Turkey threaten to scupper a 2016 deal with the EU preventing migrants entering the bloc.

This could be a major problem for Bulgaria, the EU's poorest country, since it shares a 270-kilometre (165-mile) border with Turkey.