Independent Wentworth candidate Kerryn Phelps has dismissed the prime minister's warning that a Liberal loss in the upcoming by-election could cause uncertainty, telling reporters she wants to be a stabilising force.

Scott Morrison previously told voters to think carefully about their vote, noting the risk of a hung parliament if his party loses the Sydney seat formerly held by Malcolm Turnbull.

But at the Rose Bay Summer Carnival on Sunday, Dr Phelps said it was the government that had created instability and if she won, she would be a stabilising and moderating force.