"There is an honourable member in this honourable house -- whose name I do not want to take -- he is in touch with Mansoor (Ijaz) from United States," Gilani said while speaking in the senate or upper house of Parliament Wednesday evening.
"I don't want to take his name. I have proofs. I know the person who is in touch and that is the conspiracy against the president," he said, without giving details.
Pakistani-American businessman Ijaz created a storm in Pakistan's political and diplomatic circles last month by releasing a secret memorandum that he claimed he had drafted and sent to former United States military chief Admiral Mike Mullen on the instructions of former ambassador to the US, Husain Haqqani.
The alleged memo sought US help to help prevent a military coup in Pakistan after the American military raid that killed Osama bin Laden in the garrison town of Abbottabad on May 2.
The memo further said the Pakistan government would carry out a wide-ranging revamp of the security establishment to flush out officials with links to militants.
Haqqani, who was forced to resign from his post, has denied he was involved in drafting or delivering the memo.
Gilani has asked the Parliamentary Committee on National Security to probe the "Memogate" scandal while the Supreme Court has ordered a separate inquiry.
President Asif Ali Zardari, who has been at the centre of the storm due to speculation that he was involved in the matter, abruptly left Pakistan on December 6 to seek treatment for a heart condition in Dubai.
He was discharged from the hospital on Wednesday.