Hassan Diab is set to resign within hours after the entire government stepped down.
Anti-government protesters had demanded political change after an explosion in Beirut killed more than 160 people and injured around 6,000
Lebanon’s health minister Hamad Hassan confirmed the government had resigned as he spoke to reporters after a cabinet meeting on Monday.
The cabinet has been under increasing pressure after several ministers quit or expressed their intention to step down in recent days.
Mr Hamad said: “The whole government resigned.”
He added that the prime minister will head to the presidential palace to “hand over the resignation in the name of all the ministers”.
Protests had been planned for outside the government headquarters to coincide with the cabinet meeting.