About 500 people protested against changes to pensions and welfare payments and the Coalition Government's strict new earn or learn policy for young people.

Rally organiser Ben Peelman said he was heartened by the big turnout at short notice.

He said people's anger about the budget was clear from social media.

''I've never seen so much political discourse and argument happening about one issue on Facebook,'' Mr Peelman said.

He urged the crowd to lobby Tasmanian senators to block the budget.