The government won the budget with 114 votes for, 67 against and 38 abstaining.
Speaking in parliament shortly before the budget, JVP's Wimal Weerawansa said the budget had no relief for the poor, but foreign hands were at work to topple the government.
Hours before the budget, national heritage minister Anura Bandaranaike crossed over to the opposition. Brother of former president Chandrika Kumaratunga, Bandaranaike was sacked by President Mahinda Rajapakse in February, but later re-joined the government.
Four members of the minority Sri Lanka Muslim Congress also crossed over to the opposition earlier in the week.
The JVP has supported the government's military campaign against Tamil Tigers which has scored some successes in recent months.
The JVP is also opposed to the main opposition United National Party, which st