An American businessman who has implicated Pakistan's president in an attempt to remove the country's powerful army chief claimed Thursday that security bosses were given the codename "bad boys".

Mansoor Ijaz, who is testifying to a Pakistani commission by video link from London, claimed he agreed on the secret code for the army and intelligence chiefs with Pakistan's then ambassador to Washington, Husain Haqqani.

Haqqani was sacked as ambassador over the scandal but flatly denies having anything to do with the memo, written shortly after American troops killed Osama bin Laden on May 2, allegedly because Islamabad feared an army takeover.

Ijaz told judges that Haqqani wrote him a message on his BlackBerry referring to the Pakistani government as "friend", and army chief General Ashfaq Kayani and Inter-Services Intelligence chief Lieutenant General Ahmad Shuja Pasha as "bad boys".

He also claimed that Ispahani, which is Haqqani's wife's second name, was their code word for the Americans.

Asked by the commission, what he meant by "bad boys", Ijaz replied: "they are army chief and DG (director general) ISI (Pakistan's spy service)."

Ijaz alone has implicated President Asif Ali Zardari and his testimony is considered key to any case against the president, who has faced down speculation that he could be forced out of office.

But Ijaz has refused to travel to Pakistan, citing security fears.

On Wednesday, he said Haqqani told him that the approach to the Americans had been authorised by Zardari "who wanted to put together a new national security team similar to national security team in USA".

Ijaz said he drafted the memo after Haqqani gave him points and requested that it should be delivered to Admiral Mike Mullen, then chairman of the US Joint Chiefs of Staff. The memo was delivered on May 10.

Ijaz also claimed that Haqqani said Islamabad would assist the United States "in locating other bad guys and we also commit American boots on the ground," if Kayani stepped down.

The Supreme Court ordered an investigation into the scandal following advice from the head of Pakistan's intelligence agency.

The hearing was adjourned until Friday.