Fine Gael Government Minister Charlie Flanagan and his fellow Laois TDs were warned they face trouble if Portlaoise hospital is downgraded.
Portlaoise Hospital Committee Action Group Chairman Thomas Timmons welcomed Minister Flanagan, Fianna Fáil's Sean Fleming and Sinn Féin's Brian Stanley to the anti-downgrade meeting on Saturday night.
However, he warned them of the possible punishment faced if the Minister for Health Simon Harris gives the green light to
Mr Timmons said the turnout of thousands of people sends a message.
"We are not going to take this lying down and woe betide on them if our A&E is closed," he said.
Mr Timmons praised Laois County Councillors for standing with the campaign. He thanked the public for showing up in such large numbers.
He also paid tribute to the late Kathleen O'Brien who 'gave her heart and blood for Portlaoise hospital'.