The Chamber of Deputies approved the package by 319 votes to 110, passing the law just on the day parliament dissolves for the summer recess. It will reconvene in early September.
Letta’s cabinet presented the so-called “Action Decree” in June and it has been the subject of fierce debate in both houses of parliament, where hundreds of amendments were proposed.
His broad coalition has been racked by disagreements since coming to power in April. A tax fraud conviction against former Prime Minister Silvio Berlusconi last week heightened tensions between his centre-right party and Letta’s centre-left.
This week Letta appealed to both sides to avoid a damaging political crisis, warning that an early election under the present electoral law would produce “instability and fragmentation”.
The growth package includes funding to upgrade the national rail network and school buildings, maintenance for road tunnels and bridges and measures aimed at speeding up Italy’s notoriously slow justice system.
It will also lower electricity bills by cutting a tax to fund renewable energy providers.
Letta is trying to stimulate growth and combat the longest post-war recession in the euro zone’s third-biggest economy without pushing up deficit spending.
Data on Tuesday showed the economy contracted by 0.2 percent in the second quarter, its eighth consecutive quarterly decline.