The attack in the heart of the capital on Friday killed seven people including Chatah. Hours later, the bloc implied it held Hezbollah and its ally Syrian President Bashar al-Assad responsible.
The attack comes nine months into a major political crisis in Lebanon.
Ever since a caretaker government headed by prime minister Najib Miqati resigned, the country’s main political forces have been too divided to agree on a new government.
“Today we propose a government composed of representatives of our camp and of centrists, without Hezbollah,” said Fares Soueid, secretary general of the March 14 bloc.
“We have, in the past, participated in national unity governments with Hezbollah , made compromises, initiated dialogue to try and convince this party to stop resorting to violence and killing to reach its political goals,” Soueid told AFP.
“But the killing machine has not stopped,” he added.
“Today we are calling for the creation of a government composed of our group along with centrists, excluding Hezbollah.”
The centrist bloc includes the PM designate Tammam Salam, PSP’s National struggle Front and president Michel Suleiman
PSP’s National struggle Front is headed by MP Walid Jumblatt.
Friday’s attack came amid deep tensions in Lebanon linked to the conflict in neighboring Syria.
Hezbollah has sent in thousands of fighters to back Assad’s troops, defying repeated calls to keep out of the conflict.
March 14 was created in 2005, after the assassination of former prime minister Rafik Hariri.
Assad’s opponents in Lebanon blame Hariri’s killing and that of 12 other high-profile politicians, intellectuals and security officials on the Damascus regime and Hezbollah
Although an international outcry over Hariri’s assassination forced Assad to withdraw Syrian troops from Lebanon later that year, Damascus has continued to exert significant influence through its allies.
After Mikati’s cabinet collapsd last March, pro-March 14 politician Tammam Salam was named to take his place but the country’s deep divisions have prevented the formation of a new government.
The Iranian-backed Hezbollah has proposed the formation of a national unity government, bringing together its allies, March 14 and centrist ministers.
But Hezbollah and its allies insist they must control key portfolios such as the foreign and interior ministries.