"It's just chaos for the sake of chaos," he told reporters at the Prince of Wales Hospital in Randwick.
He questioned the legality of some of the action, particularly by ferry workers. Their decision to walk off the job to protest against plans to franchise out Sydney Ferries was "an act of bastardry", he said.
Organisers had anticipated crowds of about 20,000 would join the rally against government plans to slash 5000 public service back-office jobs and impose a 2.5 per cent wages cap for public sector workers.
But Lennon told the crowd more than 30,000 protesters appeared to have turned up in response to the "unprecedented attack on public service rights".
"Friends, we have a problem, there's too many of us here," he said.
Public sector workers also took to the stage.
A prison officer called Matt railed against plans announced in the Budget to cut 350 jobs and close down three correction centres.
"Our concern is this Government will not listen until one of our colleagues is murdered," he told the crowd.
"Our message to Barry O'Farrell is you are a horrible bastard."
- AAP