Oil production fell below 1 million barrels per day in August, figures from the regulator show.
Gbajabiamila said Nigeria's crude exports were at their lowest in two decades, blaming it on crude theft that he described as "treason against our country".
"Those who seek to impoverish our country in this manner have declared war against the Nigerian people," he told legislators when reconvening the House of Representatives after a two-month break.
"The government's response must be sufficient to convince them of the error of their ways and deter others who might be tempted to join in their treason."
President Muhammadu Buhari last month expressed concern over large-scale theft of crude oil, saying it was affecting the country's revenue "enormously".
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