Deputy Liberal leader Julie Bishop has reportedly declined Prime Minister Tony Abbott's request not to attend a fundraiser event with Communications Minister, Malcolm Turnbull in Sydney on Sunday amid prospects of a leadership spill on Tuesday.

On Friday evening, after a spill motion to oust the Prime Minister was moved, Channel Nine's political editor Laurie Oakes reported the Prime Minister's office "was so concerned about the optics of them appearing together looking like a unity ticket", it asked Ms Bishop to cancel her attendance at the fundraiser with Mr Turnbull but she refused.

Ms Bishop and Mr Turnbull were confirmed as guests at a Liberal Party fundraising brunch at the historic home Rosemont, in the Sydney suburb of Woollahra, for months.

Rosemont is the home of Lady Margot Burrell which is in Mr Turnbull's electorate of Wentworth. Lady Burrell is known for her support of charities.

A number of NSW government ministers were also expected to attend the event.

On Friday, West Australian Liberal MP Luke Simpkins announced a spill motion against the Prime Minister. It was seconded by another West Australian Liberal MP, Don Randall.

Ms Bishop announced she would be supporting the Prime Minister and voting against the spill motion later Friday afternoon.

The Prime Minister's office was contacted for a response.