Montenegro calls April 7 presidential election

* Uncertainty over whether Vujanovic can run again

* Opposition to field former diplomat Miodrag Lekic

PODGORICA, Jan 18 (Reuters) - Montenegro called a presidential election on Friday for April 7, with likely frontrunner Filip Vujanovic at the centre of a row over whether he has the right to stand again for the largely ceremonial post.

Opposition challenger and former diplomat Miodrag Lekic is so far the only declared candidate in the Adriatic state that began European Union accession talks last year.

Vujanovic, the current president, is a member of the co-ruling Democratic Party of Socialists (DPS), which has dominated the former Yugoslav republic for more than two decades and led it to independence in 2006.

The presidential poll comes on the heels of an October parliamentary election, won again by the DPS despite an economic slowdown and persistent allegations of corruption.

Vujanovic, 58, tops opinion polls, but the DPS has yet to name him as its official candidate.

The opposition is threatening to challenge his potential candidacy in court, arguing that he has already served the maximum two terms. The DPS, meanwhile, says that Vujanovic has the right to another five-year term because he has held the post only once since independence in 2006.

"Journalists have repeatedly asked me whether I'll be a candidate, and I see that as a compliment that I have worked well so far and a forecast that I will surely win if I run for office," Vujanovic said this week.

The mountainous country of 680,000 people is next in line behind Croatia among the seven countries carved from socialist Yugoslavia to join the European Union, but is under pressure to root out endemic corruption and deep-rooted organised crime.