The caretaker government and Pakistan's election commission have rejected the allegations and said the country has laws and systems to investigate specific complaints.
A senior Pakistani politician, Hafiz Naeem ur Rehman, who won provincial elections in the commercial hub of Karachi, Pakistan, has given up his seat, saying the vote was rigged in his favour.
Pakistan voted in national and provincial elections on February 8 but the polls were marred by accusations of rigging to defeat independent candidates backed by jailed ex-prime minister Imran Khan, Reuters reports.
The caretaker government and Pakistan's election commission have rejected the allegations and said the country has laws and systems to investigate specific complaints.
Rehman of the Islamist Jamaat-e-Islami party was declared the winner of provincial seat 129 in Karachi after securing more than 26,000 votes.
But Rehman said he discovered that votes cast for Khan's Pakistan Tehreek-e-Insaf (PTI) party-backed independent candidate Saif Bari were reduced to 11,000 from 31,000 when records of votes polled at individual polling stations were tabulated.
Khan is in jail over corruption and criminal charges after he fell out with the country's powerful military and his PTI was barred from contesting elections, forcing members to stand as independents. The military denies meddling in politics.
"Public opinion should be respected, let the winner win, let the loser lose, no one should get anything extra," Rehman told Reuters on Wednesday.
"I will not accept it, the winner should be given the victory."
Saif Bari could not be reached for comment and the PTI said it needed time to respond. The election commission did not immediately respond to a request for comment.