GUATEMALA CITY With just a month to go before Guatemalan voters will pick a new president, the country's top court ruled on Friday to leave the frontrunner in polls out of the election.

Last week, conservative businessman Carlos Pineda was deemed ineligible to run by a lower court, but he appealed the eleventh-hour ejection from the ballot to the constitutional court.

"Corruption won, Guatemala lost!" Pineda wrote on Twitter after the decision to confirm his exclusion from the June 25 vote was announced.

Pineda's candidacy was originally suspended due to what a lower court judge cited as its noncompliance with rules governing the nomination process, such as the failure to collect signatures from party delegates and file a required financial report.

The constitutional court ruling on Friday essentially confirmed the earlier decision, while scrambling the race to succeed outgoing President Alejandro Giammattei, who is prohibited by law from seeking another term.

Prior to Pineda's disqualification, two other presidential hopefuls had previously been excluded from the ballot, prompting concern from international rights groups over Guatemala's electoral process.

Juan Pappier, an official with Human Rights Watch, branded the moves as a "clear manipulation of the judiciary" to guarantee a preferred electoral result.

Pineda led all candidates with 22% of the support in a poll published earlier this week.

With his exit from the race, the leading contenders include former first lady Sandra Torres, retired diplomat Edmond Mulet and Zury Rios, the daughter of a former dictator.

(Reporting by Sofia Menchu; Editing by David Alire Garcia)