He dominated Pakistan for eight years and became a close U.S.
ally after the Sept. 11, 2001, attacks, but ceded control of the powerful army last year and has been sidelined in government since the coalition parties trounced his allies in parliamentary elections in February.
Ruling party chief Asif Ali Zardari declared the decision Thursday was "good news for democracy" in Pakistan.
Policies pursued by Musharraf during his eight years in power "have brought Pakistan to a critical economical impasse," Zardari said.
"The incompetence and the failure of his policies has thrown the country into the worst power shortage in its history. His policies have weakened the federation and eroded the trust of the nation in national institutions," he added.
Zardari claimed Musharraf had given a "clear commitment" to resign if his party lost in the February elections and had failed to honor an indirect pledge to seek a vote of confidence from the new Parliament.
Zardari also claimed Musharraf had "conspired" with the opposition party against Pakistan's democratic transition. He made further wideranging accusations alleging misrule.
"The coalition further decided that it will immediately initiate impeachment proceedings. The coalition leadership will present a charge sheet against Gen. Musharraf," Zardari told a news conference, alongside leaders of the other coalition parties.
Impeaching a president requires a two-thirds majority support of lawmakers in both houses of Parliament. Musharraf loyalists maintain the coalition would struggle to muster it, but Zardari expressed confidence they would succeed.
"We hope that 90 percent of the lawmakers will support us," Zardari said.
Tariq Azeem, a spokesman for the main pro-Musharraf opposition party, said it would oppose any impeachment of the president.
"We have backed him and voted for him so we are duty bound to support him," Azeem said.
Azeem said he did not think the ruling coalition had the numbers in Parliament to impeach Musharraf, but conceded "things could go either way."
Announcing the joint coalition statement after two days of talks, Zardari also said the four provincial assemblies should demand a vote of confidence immediately.
The ruling coalition has a comfortable majority in the National Assembly, or lower house, but Musharraf's supporters retain about half the seats in the Senate, or upper house.
