Former One Nation leader Pauline Hanson is well placed to claim the last seat in the New South Wales Upper House.

ABC election analyst Antony Green estimates Ms Hanson has a lead of more than 6,000 primary votes over Greens candidate Jeremy Buckingham, who is also vying for the final position.

The result will be officially declared tomorrow, more than two weeks after the state election.

With 91 per cent of the vote counted, the Coalition has secured 11 of the 21 Upper House seats.

Labor has five, the Greens two, and the Shooters and Christian Democrats each have one.

Despite Pauline Hanson's primary vote lead, the Greens are still confident of winning the seat.

Greens MP John Kaye says Mr Buckingham will be better placed once preferences are distributed tomorrow.

"We have every chance of defeating Pauline Hanson on preferences," Mr Kaye said.

Before the state poll, both major parties vowed not to preference Ms Hanson, who has moved to Corlette on the state's north coast.

But the One Nation party threw its weight behind Ms Hanson, saying it still shared many views with its one-time leader.

Last year, Ms Hanson said she was selling her home and moving to the United Kingdom but later reversed her decision.

She made her name as the independent member for Oxley in Queensland between 1996 and 1998, during which time she set up One Nation.

Ms Hanson launched a failed bid for a seat in the 2009 Queensland election, in which she gained 21 per cent of the vote in the seat of Beaudesert.

She last tried for an Upper House seat in 2003.