A last-minute request for additional road works by the Roads and Traffic Authority (RTA) has pushed up costs for the already over-budget building project known as the Southern Gateway.

Costs have now reached a dizzying $11 million - $8 million of which will come from ratepayers - from an original 2003 estimate of $1.5 million.

The council has blamed the RTA, which has asked for improvements to the intersection of Bulli Pass and for the relocation of the U-turn facility, for the cost hike.

"Council is in negotiations with the RTA in respect to the increased scope of works and have adopted a conservative approach to bring all possible costs to account," a spokeswoman said.

"However, we are hopeful this may be reduced."

The controversial project has suffered consecutive cost increases since it was first mooted in 1999 by tourist groups.

Described at times as a white elephant, a bottomless pit and a waste of money, the facility has been the subject of intense debate and scrutiny because of escalating costs.

Perched high on the Illawarra escarpment, the building sits astride the busy F6 and has picturesque views of Wollongong.

It will eventually include a cultural centre, tourism office, restaurant, kiosk and viewing platform.

Business and tourism groups have consistently urged the council to stay the course with the project, which they say will eventually pay for itself, given time.

Only two months ago the cost of the project jumped $900,000 following the collapse of the Howard government's Regional Partnerships Program, which had originally promised to pay for the fit-out of an Aboriginal interpretive centre in the building.

The council hoped to replace these lost funds over 10 years by charging the Illawarra Aboriginal Corporation commercial rates for occupying part of the centre.

It comes at a time when the council is trying to turn finances around after announcing it had an $11.5 million deficit earlier in the week.

The issue will be voted on at Tuesday night's council meeting.