Wentworth by-election date announced

The by-election for Malcolm Turnbull’s seat of Wentworth will be held on October 20.

The former prime minister held the seat in Sydney’s eastern suburbs by 17 percent.

The Liberals will chose their candidate tomorrow night for what will be Scott Morrison’s first electoral test as prime minister.

Given the claims of bullying and complaints from Liberal ranks about the lack of women in parliament, there’s speculation the party will pick a female candidate.

While Mr Turnbull’s margin was large, the Liberals are expected to suffer a backlash over the toppling of their local member.

Former AMA president, Kerryn Phelps, who has a medical practice in the electorate, is expected to poll strongly if she decides to run.

Former deputy prime minister Barnaby Joyce said Mr Turnbull has a responsibility to campaign for the Liberals.

He said the voters gave Mr Turnbull his job and he should do the right thing.

He said retaining what has been a Liberal stronghold will be "tight".

Mr Joyce has previously criticised Mr Turnbull for quitting parliament, leaving the government without its one-seat majority.