Haqqani was forced to resign as Pakistan's ambassador to the US after American businessman Mansoor Ijaz made public the memo last year.
Ijaz claimed he had drafted and delivered the memo to the then US military chief on the instructions of Haqqani. The government has dismissed Ijaz's claims.
After Ijaz deposed via a video link from London, Haqqani too sought the same facility but his request was turned down. Haqqani is currently in the US and has said he cannot return to Pakistan to testify as he is being treated for a heart condition.