A conservative evangelical Christian has emerged as the front-runner to take the presidency in Costa Rica.

Fabricio Alvarado Munoz, a singer and worship leader, will face a centre-left ruling party candidate in April, after he won a first round on Sunday by sharply opposing gay marriage.

He received 24.8 per cent of the vote, while his nearest rival Carlos Alvarado Quesada received 21.6 per cent. After a third candidate dropped out they will face each other in a run-off on April 1. 

Munoz denounced a ruling by the Inter-American Court of Human Rights calling on Costa Rica to give marriage rights to same-sex couples. He described it as a violation of Costa Rica's sovereignty and an affront to traditional values. He has threatened to pull Costa Rica out of the court, which is based in the capital, San Jose.

'We propose the sovereignty of the family as the fundamental basis of society,' Munoz told supporters blowing plastic horns after the results were announced.

'Costa Rica has sent a message to traditional parties – never again will they meddle with the family.'

His opponent Carlos Alvarado Quesada supports gay marriage, making the presidential contest effectively a referendum on the divisive issue.

Evangelicals are a powerful force in Costa Rica, reflecting similar changes across Latin America.

However, statements by both the Episcopal Conference and the Federation Evangelical Alliance of Costa Rica asking Christians to 'meditate their vote before God and your conscience' were criticised as religious propaganda, according to Evangelical Focus. Costa Rica's Electoral Supreme Count issued a statement asking the organisations to 'abstain from issuing public manifestos' and stressing that 'priests and pastors are not allowed to use the pulpit, prayer places and liturgical ceremonies to induce the vote of their parishioners'.