Campaigners confident of gathering enough signatures to get a vote on overturning the decision to drill for oil in national park

Activists campaigning for a referendum on the Ecuador government's plan to drill for oil in the Yasuni national park have collected more than 50% of the number of signatures required to force the vote, and are confident they will reach the total before the mid-April deadline.

The collection of signatures is being led by Yasunidos, a newly formed group of volunteers seeking to overturn president Rafael Correa's abandonment of a plan to leave oil reserves unexploited beneath the Ishpingo-Tambococha-Tiputini (ITT) oil field in the park.

The petition requests that a referendum be held on the question: "Do you agree that the government of Ecuador should leave the crude of ITT, known as Block 43, below ground indefinitely?"

Yasuni is among the most biodiverse regions on Earth, with each hectare containing more tree species than the US and Canada combined. The region is also the last in Ecuador where indigenous groups live in voluntary isolation.

A referendum campaign would pit Correa against some of his most persistent critics, including former minister of energy and mines, Alberto Acosta.

In an upcoming article, Acosta says that the path of the Yasuni-ITT initiative reflected a "logic of permanent blackmail" by combining a threat to drill for oil with civil society's argument for the preservation of Yasuni based on ecological considerations and the rights of the uncontacted peoples.

The discovery in January last year of infrastructure developments in the comparatively oil-poor Block 31 neighbouring the ITT field proved the exploitation of Block 43 was no longer a threat but "a demonstrated certainty", Acosta writes. Ecuador officially abandoned the ITT initiative on 15 August 2013.

The country's constitutional court has unexpectedly refused to rule on the admissibility of the proposed referendum question until after the required total of signatures has been met, but volunteers say they are confident that if a nationwide vote goes ahead the government will find it difficult to counter arguments on the unique value of Yasuni that were recently its own.