Nina Ventura de Cardenas, the neighbor, says opposition lawmaker Miro Ruiz shot and killed her 18-month-old dog when it ventured onto his property. Ventura filed a formal complaint with Congress on Monday.
Ruiz denied the allegation, saying he has several small animals and "loves them a lot."
But animal rights activists and fellow politicians called for sanctions.
Cabinet chief Jorge del Castillo said the alleged killing of the pet demonstrates "psychological weakness" and "hurts the country."
The congressional ethics committee will review the complaint.
