"According to the new system we have proposed, the president will be held accountable to the parliament. The cabinet of ministers is also accountable to parliament," Wickremesinghe said in a televised address.
The proposal could take several weeks to be approved, as it needs to be accepted by the cabinet and the Supreme Court, after which the parliament's approval will be sought.
President Gotabaya Rajapaksa and his brother, Mahinda, rolled back a series of electoral, police and financial reforms enacted by the previous government, months after assuming power with a two-thirds majority in 2020.
Opposition leaders had accused the Rajapaksa government of disproportionately increasing presidential powers and diluting the role of the parliament in lawmaking.