Monster Trucks Australia organiser Clive Featherby said they had to turn away at least 6000 people from the showground gates after tickets sold out.

He said police had to be called in to deal with angry parents who had travelled to Newcastle only to be turned away, and the ensuing gridlocked streets in surrounding suburbs.

Showground managers said the number of people turned away was closer to 200 and Mr Featherby was free to schedule extra shows.

Newcastle Showground holds about 6000 people but held more than 13,500 people on Saturday night after organisers brought in portable grandstands.

"When you're turning people away and you're turning away little kids it gets very hostile," Mr Featherby said. "We had to call police in to calm problems at the gate. It was absolute pandemonium."

The show visits Newcastle once each year and Mr Featherby said they would like to put on more than one show but were prevented by "a couple of neighbours" who complained about the noise.

"We finish normally by about 9.30pm so I hope something can be done," he said.

They turned away bus loads of people from Taree because it was no longer cost-effective to take the show to smaller towns, he said.

Newcastle showground and entertainment centre general manager Chris Blanch said the Hunter Region Sporting Venues Authority would plan improvements to the showground in its long-term master plan.

But he said it was not feasible to upgrade the stadium to cater for once-a-year events.