Ms. Bhutto has given mixed signals about whether she would work with President Musharraf since he imposed emergency rule on November 3. But after being placed under house arrest Tuesday in Lahore, Ms. Bhutto gave the clearest denunciation yet of her political rival.
In a phone interview with Sky news, Ms. Bhutto said General Musharraf's autocratic rule had undermined the war against militants who are destabilizing Pakistan and Afghanistan.
"And that's why we say Musharraf must leave. The time for dictatorship is over," she said. "It was tried and it failed to contain militancy."
In interviews with other news agencies, she said she would not serve as prime minister under President Musharraf.
The president has said the government plans to hold elections on schedule in January, but he has also insisted that military-enforced emergency laws that suspend basic rights will not undermine those polls.
Opposition parties have rejected the claim and said they will boycott the elections if emergency rule is not lifted. Ms. Bhutto Tuesday suggested her party might join them.
President Bush has said the emergency order must be lifted to ensure free elections.
General Musharraf has defended the thousands of arrests of protesting lawyers and rights activists under the emergency laws as necessary to preserve law and order.
In Lahore on Tuesday, hundreds of security forces used barbed wire, steel barricades and dump trucks loaded with sand to hold back people trying to reach Ms. Bhutto.
Benzair Bhutto is the former Prime Minister of Pakistan. She has been placed under house arrest ahead of a planned protest march against the state of emergency imposed by President Pervez Musharraf. So far, Musharraf has been able to prevent large-scale rallies against him, silencing the many who are calling for him to step down.