Prime Minister Tony Abbott's sister, Christine Forster, has launched a bid to be elected to the NSW upper house at next year's state poll.

Councillor Forster, who is on the City of Sydney Council, has nominated to be preselected to a winnable position on the Liberal Party's upper-house ticket.

Nominations for three "at large" upper-house positions – those without direct responsibility for geographical areas – close in October.

Party sources anticipate two positions are definitely winnable and possibly a third – the 10th position on the joint Coalition ticket – if the vote holds up better than expected.

Cr Foster, who is factionally unaligned, will likely have to battle it out against a former City of Sydney councillor, Shayne Mallard, who is expected to be the Left faction's candidate. Mr Mallard unsuccessfully contested the 2012 byelection for the state seat of Sydney.

Former NSW Young Liberal president Scott Farlow is believed to have strong support from the centre-Right faction to be preselected for the second winnable spot on the ticket.

It is understood that Neil Harley, a former lobbyist who helped run federal MP Craig Laundy's campaign for the seat of Reid, is also considering a tilt.

In Cr Forster's favour is that the Liberals have been criticised over the prospect they may run an upper-house ticket without a single woman at next year's election.

The party has chosen candidates for its "provincial" spots on the ticket – those with responsibility for particular regions – and none has gone to a woman.

Cr Forster's decision to nominate has come as a surprise to some who assumed she was focused on being chosen as the Liberal candidate for Lord Mayor of Sydney in 2016, following the NSW government's overhaul of City of Sydney council election rules to give businesses two votes.

The state government has been accused of introducing the legislation to help it topple independent lord mayor Clover Moore, who is considering whether she will recontest the job.

Liberal preselection candidates are forbidden from speaking to the media. Cr Forster did not respond to a request for comment.