"This is not the first time lawmakers have taken part in horse trading," Khan said. "This has been happening for the past 30 or 40 years."

The PTI chief said that the accused lawmakers had received as much as Rs40 million each and added that the party will issue a show-cause notice to them.

Khan lauded other members of his party who "resisted the temptation" to take large sums of money offered to them by other parties.

Last month, Dawn.com had learned that at least 17 PTI lawmakers in Khyber Pakhtunkhwa allegedly sold their votes during the Senate election enabling two PPP candidates to be elected to the Senate from the province where the PPP only has seven MPAs.

An initial investigation ordered by KP Chief Minister Pervez Khattak into alleged horse-trading had revealed that at least 17 ─ and as many as 20 ─ PTI MPAs in KP had voted for candidates outside the party, sources in CM House Peshawar and Bani Gala had told DawnNewsTV.

Additional reporting by Fahad Chaudhry.