Health Minister David Davis has escalated his attack on the paramedics union, accusing it of further misrepresenting waiting times at hospitals.

Mr Davis accused the union of at the Frankston Hospital in July to overstate waiting times.

The union denied the photos were staged and said the hospital was chaotic on the night in question.

The Ambulance Employees Association also said there were more cases of ambulance ramping on Thursday night at the Alfred, Royal Melbourne and Northern Hospitals.

Mr Davis says that is not true.

"I'm informed that there were no delays at those hospitals," he said.

"They made claims also last night about the Geelong region. I'm also informed that those claims were not true."

The ambulance union is in the middle of an industrial dispute over pay with the state government.