Reacting to reports that Zardari, who is at the centre of the controversy, may bow out, Farhatullah Babar described them as "totally speculative".
The reports in 'The Cable'-- a blog of prestigious US magazine 'Foreign Policy' - had said Zardari, who had gone to Dubai for treatment, would not return, apparently giving in to intense heat put up by the powerful Generals.
Zardari, 56, left for Dubai yesterday on a private visit to meet his children and undergo some medical tests, officials reports had said.
But, The Cable quoting unnamed officials from the Obama administration said there is growing expectations inside the US Government that Zardari may be on the way out.
A former US official told the Cable that parts of the US government were informed that Zardari had a "minor heart attack" on Monday night and flew to Dubai via air ambulance.
He may have angioplasty today and may also resign on account of "ill health", said the blog, which has been filing a series of stories on Pakistan related to memogate.
Zardari's trip comes as he has come under pressure over the memogate scandal that had forced Pakistani Ambassador to the US Hussain Haqqani to resign.
"All these media reports are totally speculative. The President is in a hospital in Dubai for medical tests and a check-up as already planned," Babar told PTI.
He did not give details of the medical tests or the President's plans to return to Pakistan.
Reports in sections of the media speculating on the President's "activities and engagements are speculative, imaginary and untrue", the presidency said.
Zardari travelled to Dubai after holding meetings with Prime Minister Yousuf Raza Gilani, Senate Chairman Farooq Naek and Interior Minister Rehman Malik.
Babar had then quoted the President's personal physician as saying that the medical tests were of a routine nature and linked to a "previously diagnosed cardiovascular condition".
Sources close to Zardari told Geo News that reports about him resigning due to ill health were untrue and that he was expected to return to Pakistan after the medical check-up.
The channel further quoted doctors at the Dubai hospital as saying that there was nothing of concern in Zardari's preliminary medical reports.
Much of the speculation about Zardari's activities had centred around a report on the website of 'Foreign Policy', which contended that he intended to step down due to mounting pressure on him because of the memogate controversy.
The report claimed, "The noose was getting tighter -- it was only a matter of time," signalling that Zardari may be facing intense heat from the powerful army to quit.
It quoted Shuja Nawaz, director of the South Asia Center at the Atlantic Council, as saying, "This is the 'in-house change option' that has been talked about."
Nawaz said that this plan would see Zardari step aside and be replaced by his own party, preserving the veneer of civilian rule but ultimately acceding to the military's wishes to get rid of him, the report said.
"Unfortunately, it means that the military may have had to use its muscle to effect change yet again," said Nawaz. "Now if they stay at arm's length and let the party take care of its business, then things may improve. If not, then this is a silent coup" with Pakistan Premier Yousuf Raza Gilani as the front man, he said.