The National Assembly seat NA-149 was vacated following the resignation of Makhdoom Javed Hashmi, the former president of Pakistan Tehreek-i-Insaf (PTI).
Hashmi again contesting election from the same constituency as an independent candidate.
The province requested the Election Commission of Pakistan (ECP) to put off the by-election citing security reasons.
Provincial election commission has opposed the government request, sources said.
By-polls in NA-149 are scheduled to be held on Oct 16.
According to sources, the provincial government has requested for postponement of the by-election in view of the situation after deaths in a stampede in Multan public meeting of PTI.