Prime Minister Shinzo Abe denied Tuesday the possibility that he or his office was involved in a controversial survey that oppositional parties claim was aimed at making a so-called discretionary labor proposal look like a system that could improve the nation’s overwork problem.

Abe's remarks came as the ruling Liberal Democratic Party has been under fire in the Diet over an envisioned bill to expand the labor system under which employees are given a fixed number of overtime hours and are paid on the assumption they work those hours.

The contentious survey, conducted in 2013 by the Health, Labor and Welfare Ministry, said the average worker on a discretionary labor contract generally works shorter hours than one on a conventional contract.