The evangelical Christian Fabricio Alvarado Muñoz has maintained his lead in Costa Rica's second-round presidential race even as his centre-left rival narrowed the gap, according to a poll published yesterday.

The controversial religious singer and former journalist has 55.1 per cent of voter support ahead of the April 1 election compared with 44.9 per cent for former minister Carlos Alvarado Quesada, said a survey by OPol Consultores.

The 10-point difference between the two rivals compared with a 14-point difference in last week's poll.

The poll of more than 2,200 people was conducted between February 15 and 16, and has margin of error of 2.1 percentage points.

Alvarado Muñoz's rise on a ticket fiercely opposing gay marriage was helped by the decline of a centrist two-party system that stretched back decades in a country long considered one of the most stable in Latin America.

Muñoz was elected to the national assembly in 2014 as the only federal deputy representing the Christian-backed National Restoration Party (PRN).

Latin America, which is traditionally Catholic, has seen a steady rise of evangelical churches in recent years.

However, recent 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'.

Additional reporting by Reuters.