Pakistan's opposition has demanded President Musharraf seek parliament's approval for sweeping powers he awarded himself last year.
Senators from an Islamist alliance of the Muttahida Majlis-e-Amal (MMA), Pakistan Peoples' Party (PPP) and Pakistan Muslim League-Nawaz (PML-N) thumped desks and chanted slogans against Musharraf before walking out of the senate chamber on Thursday.
The combined opposition is running a relentless campaign in both houses of parliament to force Musharraf, who appointed himself president in June 2001, to face a presidential election.
They have been boycotting parliament since its first sittings in February this year.
"Our protest in the parliament will continue until the government brings a constitutional amendment package before it and Musharraf gets himself elected from the parliament," MMA Senator Maulana Shah Ahmed Noorani said.
General Musharraf, also Pakistan's army chief, gave himself sweeping powers under constitutional amendments he introduced just two months before the end of his three-year
Musharraf (R) appointed himself
president after taking over the
country in a coup
The powers include the right to sack the elected parliament and to hold the dual posts of army chief and president until 2007.
The amendments also gave the armed forces an unprecedented role in governance under a civilian-military National Security Council.
The bitter standoff over the amendments has kept the first parliament since Musharraf's coup in limbo.
In 11 months since it was elected it has passed no bills other than the national budget.
While religious parties are ready to accept Musharraf in military uniform for a limited period, the PPP and PML-N of former prime ministers Benazir Bhutto and Nawaz Sharif respectively are determined to have a civilian ruler.
"Whether in uniform or without it, General (Musharraf) is not acceptable to us, or his constitutional amendments," PML-N senator Ishaq Dar said.