The proposal, which would double the size of the Coles supermarket and expand the plaza with buildings up to three storeys tall, is on public exhibition until Wednesday.

Mr Jones said it would remove all on-street parking - all of King St and both sides of Lawrence Hargrave Drive from the Commonwealth Bank to Raymond Rd - which main street traders depend upon.

He said the impact on traders would be "tragic".

"If it went ahead as it currently stands, if your business wasn't in the plaza, you'll be out of business," he said.

Read more: $60m development proposal lodged, including 82 apartments

"Why have an effective clearway [in] the busiest pedestrian precinct, when at either end, the road narrows to one lane each way? It will just make for a wider traffic jam and wipe out all traders outside the mall."

He said it should not have proceeded so far given the three-storey buildings don't fit the two-storey Thirroul limit in Wollongong's Development Control Plan (DCP).

"The DA did mention numerous planning meetings with the council staff," Mr Jones said.

"Isn't it up to the [staff] at Wollongong City Council point out the two-storey limit and to say that if they want three storeys then they need to get the Wollongong DCP changed?"

The developer's spokeswoman, Brisbane-based marketing professional Emma Foster, said traffic estimates were being overstated.

She said the predicted 550 vehicle movements both morning and evening peaks, and more than 730 on weekends, actually included present-day traffic.

"The Traffic Impact Assessment which was conducted by an independent traffic consultant, stated the current retail area at Thirroul Plaza is generating over 300 vehicle movements in morning and afternoon peaks and there is already a need for King Street to be signalised, so if the development proceeds the traffic lights installed will greatly alleviate the existing road conditions," she said.

The developer Thirroul Plaza Pty Ltd is owned, through a series of holding companies, by Austinmer engineer Angelo Forte of Mainland Civil, Austinmer builder Mark Forte, of the Genesis construction company, and a Queensland-based company called Blue Sky DLS, itself owned by investors from Sydney and Queensland.

Mainland Civil Holdings itself has several shareholders, in addition to Mr Forte and his partner Robert Dahan, from the Sutherland Shire and Queensland.