In a statement, the Election Commission of Pakistan said it issued notices to heads of political parties and lawmakers on the basis of their statements in media about corruption in elections.
It said that they "have been summoned on March 14 to initiate an investigation" into their claims about massive use of money. Action will be taken against those found guilty, it added.
Provincial and federal lawmakers voted to elect 52 Senators in the Senate elections on March 3.
PML-N Quaid (chief) Nawaz Sharif blamed those political parties that secured more seats than their representation in the provincial assemblies for "rigging the Senate elections" and demanded an investigation to ascertain if the change of loyalty was based on change of mind, financial gain or some other factors, Dawn reported.
The former prime minister said the game of trading of votes must come to an end.
The same demand was made by Pakistan Tehreek-i-Insaf chairman Imran Khan on the second day of his two-day visit to Karachi for a party membership drive.
Khan said that according to his information votes were purchased for up to Rs 40 million in the Senate elections.
"Our own people also sold themselves," he admitted but did not mention names of those allegedly involved in the practice in Khyber-Pakhtunkhwa and Punjab assemblies.
He said his party had been asking the Election Commission of Pakistan to replace the old secret ballot system with open voting for Senate elections to help check corrupt practices, but the ECP did not accept the demand.
It was for this reason that the lawmakers had indulged themselves in trading of votes, he alleged, while asking the ECP, National Accountability Bureau and Federal Investigation Agency what actions they had taken to check the horse-trading.
He demanded that Chief Justice Mian Saqib Nisar take notice of the horse-trading, explaining that those who had bribed the lawmakers were known but the legislators who had allegedly taken bribe to switch loyalty were not traceable.
The Muttahida Qaumi Movement-Pakistan (MQM-P), which suffered a major setback in the election, announced that it would challenge the Senate elections in the ECP and courts, accusing Pakistan People's Party (PPP) and Pak Sarzameen Party (PSP) of "harassing" MQM lawmakers and "selling" the mandate of Karachi.
While addressing a press conference, Dr Farooq Sattar, heading the PIB faction of the MQM-P, said the Senate elections lost credibility as they were not held impartially and transparently.
He alleged that the PPP harassed more than 15 legislators of his party in order to pressure them to change their loyalty. He also accused PSP chief Mustafa Kamal and his deputy of "selling" the mandate of Karachi.
The election results for 12 Senate seats from Sindh have surprised many. Farogh Naseem, who supports the Khalid Maqbool Siddiqui-led faction of MQM, is the only candidate of the party to have emerged victorious for the upper house of the parliament.
Just a day ago, Jamaat-i-Islami chief Senator Sirajul Haq, too, had demanded investigation into the allegation of horse-trading. He also appealed to the chief justice to take notice of the Senate election where parliamentarians allegedly cast votes for financial gains and other benefits.
(This story has not been edited by Business Standard staff and is auto-generated from a syndicated feed.)