Google is still on the hunt for a new Australian headquarters after the New South Wales Government rejected a proposal that would have seen it anchor a new Silicon Valley-style technology hub in Sydney.

It is the second time in a year that Google's search for a new home in the harbour city has hit a stumbling block, and now there are warnings the company could be driven interstate.

Late last year developer Mirvac submitted a unsolicited proposal to the Government to build a technology hub next to the Carriageworks at Eveleigh, with Google as the anchor tenant.

The company envisioned a mixed-use development that would create thousands of jobs and include an upgrade of Redfern station and a new land bridge linking the Australian Technology Park to the Eveleigh site.

But the Government has now decided not to go ahead with the proposal, preferring a competitive tender process instead.

Google has declined to comment, but Mirvac said it "remains firmly committed to working closely with the Government to realise the vision".

The developer called the hub "world class" and "innovative" with housing diversity, public spaces and sustainable outcomes.

Acting New South Wales Premier John Barilaro said the Government rejected the blueprint because it was not "unique".

He said it did not meet the Government's criteria for an unsolicited proposal and that it wanted an open tender for the site instead.

"The Government determined that the actual idea was not unique in itself," he said.

"The idea that Google is part of it is fantastic. We're not knocking back the idea, all we're saying is that it will have to go to an open-market process to make sure we get the best return on investment for that site."

Google rejected first site for insufficient transport

An artist's impression of the White Bay Power Station redevelopment which Google backed out of. ( Supplied: NSW Government )

The decision comes a year after Google delivered a big blow to the Government's plans to convert the old White Bay Power Station into an international technology hub.

The Government had hoped Google might be an anchor tenant but the tech giant rejected the site as a potential headquarters, saying it did not have enough transport links.

Google is currently based in Pyrmont, opposite the Star Casino, and it is here where most of its Australian workforce is based and where the technology behind Google Maps was created.

State Opposition Leader Luke Foley has questioned the Government's commitment to securing tech jobs for NSW.

"My fear is that Victoria will sneak in under our state's guard and attract these jobs," Mr Foley said.

"This is a missed opportunity for Sydney, we should be attracting the high-tech jobs of the future but the Government seems disinterested."

Plans submitted through the Government's unsolicited proposals process have traditionally struggled to be approved.

Pitches that were given the greenlight in recent years include the NorthConnex project and James Packer's unsolicited proposal for a VIP Casino and luxury hotel at Barangaroo.