This is the NDP's second demand to the Liberals, who need the NDP's support to pass their budget and avoid an election. Earlier this week Horwath called on the Liberal government to create a financial accountability office to track government spending.
Premier Kathleen Wynne called the idea of an accountability office "an interesting idea" but has yet to meet with the NDP leader to discuss it further.
Horwath says she the ombudsman should have authority to examine complains against hospitals, ambulance services, nursing homes and retirement homes.
"I don't blame people for not believing Liberal promises anymore," said Horwath. "Their system of just throwing millions at a problem and saying, 'just trust me' hasn't delivered results. It's given us eHealth, Ornge and other health care scandals."
The ombudsman would also help ensure that the Liberals meet her demand for a five-day guarantee for home care, Horwath said.
Horwath says there will be more demands next week.
The Conservatives have been clear they are hoping for an election.
"I think there's never a problem with having more oversight across government ... but we need to start at the top," said Progressive-Conservative MPP Monte McNaughton. "We need to change the team that's leading the province of Ontario."