TORONTO -- Premier Kathleen Wynne is downplaying problems with a new computer system that erroneously queued up $20 million in overpayments to welfare and disability support recipients last week.

Wynne admits there was a "glitch" with the $240-million Social Assistance Management System (SAMS), but says 99 per cent of the bad cheques were stopped and corrected within 24 hours.

She says most overpayment errors were quickly addressed, and only about 100 cheques still need to be corrected.

Wynne also says everyone who was expecting a benefit cheque last week got one.

The premier says the computer that sends out more than 500,000 cheques every month was outdated and in need of an upgrade, and 11,000 workers were trained in how to use the new system.

The Ontario Public Service Employees Union warned the government last summer that the new SAMS computer system would not be ready to go online this fall.

Both the Progressive Conservatives and New Democrats accused the Liberals of mismanaging the overhaul of the welfare computer system.