Due to the "sensitivity of the charges" levelled by Ijaz, including the alleged authorisation of the memo by President Asif Ali Zardari, the highest level of Pakistan's military leadership decided the initial investigation must be carried out by the ISI chief, 'The News' daily quoted its sources as saying.
Asked to confirm whether the official who met him on October 22 was Pasha, Ijaz told the newspaper: "Yes."
Ijaz earlier said that the full data and evidence of his contacts with the Pakistani official who asked him to draft the memo has been given to Pakistani authorities. This includes records of phone calls, SMS messages, Blackberry exchanges and emails.
The News reported that Ijaz met Pasha on October 22 in Park Lane Intercontinental Hotel in London.
The meeting lasted for over four hours and Ijaz was "exhaustively grilled over his claims", the report said.
The material provided by Ijaz was "subsequently put through a verification process" and once Pasha was convinced about its authenticity, "he briefed the army chief (Gen Ashfaq Parvez Kayani) who ultimately discussed the matter in his one-on-one meeting with President Zardari on November 15".
Kayani "impressed upon the President the inevitable necessity" of the presence in the country of Pakistan's Ambassador to the US Husain Haqqani to explain his alleged role in the controversy.
After the Zardari-Kayani meeting, the presidency announced that Haqqani had been called to Islamabad to explain his position.
"According to sources, the President had been fairly confident about stubbing out the matter for good in his one-on-one huddle (with Kayani) but the outcome was not entirely to his satisfaction," the report said.
Prime Minister Yousuf Raza Gilani called Kayani and set up a meeting of the President, Premier and army chief on November 16.
Gilani, known for "not harbouring any exceptional love" for Haqqani, also said in Parliament that "ambassador or no ambassador, he will have to come and explain his position".
The presidency's decision to act on the controversy was due to an official communication sent to Zardari over the weekend before his meeting with Kayani.
"In this communication, the President had reportedly been specifically requested to order an enquiry into the memo issue," the paper said.
The report further said Haqqani will present his viewpoint in a meeting attended by the President, Premier, army chief and ISI chief.
"The Ambassador will be required also to respond to a set of questions already prepared in this regard, including why he has not even given an indication of suing Mansoor Ijaz for defamation and slander," the report said.
The Pakistan government might officially contact the Blackberry company to obtain certified data and "spare no influence, including cessation of Blackberry services in Pakistan, were the company to act reluctant in complying with the request," the report said.