The protesters were rallying on Wednesday against government plans to revise employment laws that businesses say tilt too far in workers' favour, making Indonesia uncompetitive and inciting investors to place their funds elsewhere.
More than 30,000 people took part in the Jakarta rally, the latest of a series of protests by unions demanding the government drop its attempt to modify the 2003 labour law.
Some carried posters demanding Susilo Bambang Yudhoyono, the Indonesian president, and Jusuf Kalla, the vice president, resign over what the government says is an attempt to make the industrial climate friendlier to investors.
Workers have been lobbying several legislators, seeking confirmation they will oppose the government's proposed changes when they are put before parliament.
Syukur Sarto, who heads the Confederation of Indonesian Workers' Unions (KSPSI), told news channel Metro TV after meeting legislators: "Some of the parliamentary leaders have agreed to not revise the law.
"However, we want such a statement to be made on behalf of the entire parliament."
Government allies say such a demand is wishful thinking.
Charles Mesang of Golkar, the party with the most seats in parliament, said: Some of my colleagues have stated that they would reject the revisions. But that's at the personal level." He was referring to opposition politicians who sit with him in the labour and health commission.
The government and many of its supporters in the chamber, elected in 2004, want to amend the law to give employers more flexibility, curb strikes and ease back on severance payments for sacked workers, currently among the world's most generous.
Opponents want Susilo to step
down as president over the law
But after the initial wave of protests over the issue last month, the government said it would have academics review the draft and hold further discussions with labour and business.
KSPSI's Sarto said protesters had begun to disperse after his meeting with legislators ended. Most rally participants came from KSPSI, he said.
KSPSI, one of Indonesia's leading labour groups, did not join the May Day rallies that ended without major incident on Monday, choosing to hit the streets on Wednesday instead.