According to local media, Pedro Briones was shot dead by gunmen on a motorcycle at his home in northern Esmeraldas province, a notoriously lawless area.
His killing comes just five days after presidential candidate Fernando Villavicencio was gunned down in the capital, Quito.
Ecuador’s murder rate has surged as local gangs have forged alliances with international crime cartels.
Mr Briones was a leader of the left-wing Citizen Revolution Party in Esmeraldas. Fellow members of the party expressed their condolences to his family.
Former president Rafael Correa, who founded the Citizen Revolution Party, wrote: “They murdered another of our colleagues in Esmeraldas. Enough is enough!”
Police have not yet officially commented on the murder but local media reported that the two gunmen had fled on a motorbike after shooting dead Mr Briones in San Mateo, south of the city of Esmeraldas.
It is not yet clear what the possible motive may have been.
Esmeraldas province, on the border with Colombia, has been one of the worst hit by the wave of violence which has spread across the country.
Its porous border with Colombia and its location on the Pacific coast makes the province attractive to drug smugglers who traffic cocaine from Colombia through Ecuador to the US and Europe.
But the violence has not been contained to Esmeraldas. Last month, the mayor of the port city of Manta in Manabí province was shot dead as he was inspecting a public works project, and a few weeks earlier a mayoral candidate in the beach resort city of Salinas was shot to death.
The highest-profile victim so far has been Fernando Villavicencio, an outspoken journalist who had uncovered corruption scandals and denounced links between organised crime and government officials.
Six men have been arrested in connection with his assassination, all of them Colombian citizens.
FBI agents arrived in the country from the US on Sunday and have joined forces with Ecuadorean police to investigate Fernando Villavicencio’s murder.
Sources: BBC, El Universo.